434 - ■ 'CHELONIA. 



fig. 3, that a more minute description of them is not deemed neces- 

 sary. The saQie is the case regarding the plates on the sides of the 

 head, exhibited in ^g. 4 : five temporal shields (or plates), of consider- 

 able development, may be seen : three in front, one above, and one 

 below the tympanic region, properly so called, and which is covered 

 by plates a good deal smaller. On the sides of the lower jaw, there 

 are four irregular plates of moderate size, and about half a dozen of 

 smaller ones, which approximate the angle of the mouth. The mental 

 shields are small, four in number, disposed upon a transverse series, 

 contiguous to the horny sheath of the lower jaw. The rest of the chin 

 exhibits an indurated epidermis variously plaited. 



The color is dark reddish-brown above, and yellowish-brown be- 

 neath. The cephalic plates are reddish upon their middle region, and 

 yellowish at their periphery. 



Log. — The specimen figured was collected at Madeira, in 1838, on 

 the passage out of the Expedition. 



Plate XXIX, fig. 1, represents ThalassocheTys corticata, in profile. 

 Fig. 2, exhibits the same animal from below. 

 Fig. 3, is an upper view of the head ; and. 



Fig. 4, a side view, with the mouth open, in order to exhibit the 

 outline of the jaws. 



All these figures are drawn half the natural size of the specimen. 



Genus LEPIDOCHELYS, Fitz. 



Gen. Char. — Head moderate ; anteriorly compressed ; snout rather 

 protruding; jaws sharp and even upon their margin, curved towards 

 one another at the tip. Eye moderate. Two pairs of frontal plates, 

 a vertex plate, and three pairs of parietals. A middle occipital, 

 moderate, sometimes subdivided ; two pairs of latero-occipitals ; one 

 pair of postoccipitals and occasionally a few small additional ones. 

 Three postoculars. Carapax subcordate, or subelliptical, ample, 

 posteriorly indentated upon its periphery, covered with seventeen 

 to twenty-one unimbricated shields, ridged in the young, smooth in 

 the adult. Marginal shields, twenty-seven in number. Plastron 



