on the Anatomy of Whales, it must, nevertheless, have been known to several. If we find that the terminal epiphysis has become completely united to the body of the vertebra, we may be assured that the bone, whether large or small, belonged to an animal arrived at maturity; but if not, we may conclude that it had not yet attained to its greatest size. To facilitate this inquiry, I may remark, that a very slight examination of a vertebra is sufficient to determine, whether the epiphysis has or has not been detached; as in the former case the surface is marked by deep ridges and furrows diverging from the centre towards the circumference; whereas in the latter, if the animal was of moderate size, the marking consists of concentric lines, answering to the attachments of the intervertebral substance; and if the individual was very large, these concentric lines are exaggerated into concentric furrows; and whether the attachments of the intervertebral substance be marked by concentric lines or by concentric furrows, a considerable portion of the central part of the bone, where it had been in contact with the internal substance of the intervertebral ligaments, is quite destitute of this marking, and presents a striking contrast to the rest of the surface.

I am not aware that the true cause of this remarkable difference between the markings on the extremities of the vertebræ of the cetacea has been before explained.

It may not be uninteresting to add, that the cranium of the Delphinus diodon in my possession, and both those in the Museum of the College of Surgeons, present, in a very remarkable manner, the want of symmetry between the right and the left sides of the cranium, which was first observed by Meckel in the skulls of the cetacea.

Note. Since the preceding notice concerning the hock-joint of the horse, was submitted to the Academy, I have had an opportunity of examining two horses affected with string-halt, and am inclined to attribute the disease to a spasmodic affection of the flexors of the limb generally, rather than to any derangement in the structure of the hock-joint. It may be right to mention, that the following authors on Comparative Anatomy, and the Anatomy of the Horse, have been searched, but they contain no notice of the peculiarity in the structure of the hock-joint, above described :—Macartney, Cuvier, Carus, Blumenbach, Meckel, Clater, Blaine, Stubbs, Percivall, Boardman, White, Lawrence, Osmer, Home, Bourgelat.

Unknown

SEA

On the Lacustrine Basins of Baza and Alhama, in the Province of Granada in Spain. By Colonel SILVERTOP, M. G. S. L. Communicated by the Author.-(Concluded from former volume, p. 349.) With a Plate.

BASIN OF ALHAMA.

THE geographical position of this basin was alluded to in general terms at the commencement of my last communication. It occupies a large circular area, at the distance of about fifty miles to the south-west of that near Baza, on the northern side of the primitive and transition chain of mountains which border the Mediterranean; and it is chiefly surrounded by primary rocks towards the south and east, and by ridges of secondary limestone towards the north and west *. In the latter, close to a town called Loja, at the western extremity of the basin, there is a chasm through which the river Genil †, rising in the Sierra Nevada to the east of Granada, is enabled to escape, and to pursue its course to the Guadalquivir; but beyond this chasm the secondary limestone is continued, and, circling round towards the east north-east, forms the boundary of the basin towards the north. A considerable portion of this ridge is known by the name of Sierra de Cogollos, and the distance from it to the opposite ridge near Alhama, may be taken as the greatest length of the basin; that from a village called Escuzar, on its eastern side, to the town of Loja, as its greatest breadth; the former being equal to about thirty-six, the latter to about thirty miles. One insulated group of transition limestone, named La Sierra de

* In the southern boundary of this basin, a junction between the primary and secondary rocks occurs between a pass called El Puerto de Zafarraya and the western flank of a high mountain, well known to botanists, and called La Sierra de Tejeda: in the northern boundary a similar junction takes place, near a village called Huetor de Santillana, about four miles from Granada, on the road to Guadiz. At neither of these points, however, is there any interruption of continuity in the bounding ridges, the secondary limestone in both instances appearing to come in contact with, and to rest upon, primary rocks of a similar composition or basis; that near Huetor being a granular, that of Tejeda a lamellar limestone, and both highly crystalline.

+ The classic vale, the Vega de Granada, watered by the Genil, has been immortalized in song and in prose, as the theatre of many a chivalrous deed in the olden times.

OCTOBER-DECEMBER 1830.

E

Elvira, near Granada, is seen within this area: with this exception, the whole of its superficies is occupied by conglomerates, marl, gypsum, and other tertiary beds; the conglomerates predominating to the north and east of Granada, and forming a high tract of waving hilly ground between this city and the Sierra Nevada; the latter prevailing to its south, or from the left bank of the river Genil to the ridge which confines the basin in the latter direction. The upper stratum of the valley of the Genil, which occupies the lowest relative tract in this basin, is generally composed, near Granada, of a disintegrated conglomerate, an argillaceous marly deposit, with innumerable rounded fragments of the neighbouring primary and transition rocks; but lower down it often consists of a sandy loam. The rising ground from this valley in the direction of a village called Cogollos, situated at the base of the ridge which bounds the basin towards the north, exhibits a high, broken, irregular tract, consisting of a calcareous marly deposit, with some beds of marly sandstone two or three inches thick, and containing, as I was informed, some beds of lignite *. Near Alfacar, another village upon this slope, there is an extensive formation of calcareous tufa, which is quarried, and has furnished the material with which several of the churches in Granada have been built + it passes in some places into beautiful alabaster, which receives the most brilliant polish, and is worked into slabs, vases, and other ornamental figures.

There is one circumstance perhaps worthy of being noticed, connected with the conglomerate hills between Granada and the Sierra Nevada. A stream called El Daro, taking its rise near the village of Huetor de Santillana, and entering the Genil at Granada, winds its intervening course between high hills of this deposit. After heavy rains have increased the volume and rapidity of its waters, and transported to its bed the loose materials of the adjoining hills, it is not unusual to find particles of gold disseminated in the sand and mud deposited after the tor.

I had no opportunity to examine this tract, but presume it to be tertiary. + Extensive deposits of calcareous tufa are observable in many parts of the south of Spain, generally along the bases of limestone ridges. Natural excavations in these constitute caverns, often of singular beauty; that called St Michael's at Gibraltar, is well known.