84 



BRITISH FOSSIL REPTILES. 



pectoral paddle ; but the still smaller proportion of the pelvic one suggested the nomen 

 triviale, which is vindicated, also, as a sign of specific difference, by the proportionally 

 sliorter and thicker jaws and by the modification of the vertebral centrums (Tab. XXIX, 

 tigs. 2 and 7) ; in this character the present species differs from Ich. hreviceps. 



Ich. latimanus resembles Ich. communis in the ventricose, subobtuse character of the 

 teeth, or, at least, some of the more worn ones, of the twenty-nine which may be counted 

 on each side of both jaws. The articular surfaces of the centrum are concave at the 

 middle third, the rest of the surface to the circumference is flat. 



In the specimen of Ich. latimanus, 6 feet 10 inches in length, and in that of an Ich. 

 communis, 5 feet 2 inches in length, the following were the respective dimensions of 

 bones of the scapular arch and its appendage : 



Scapula, length of . . 

 Coracoid, antero-posterior diameter 

 Coracoid, transverse diameter 

 Antibrachials, breadth of . 

 Length of fore fin, humerus inclusive 

 Breadth of ditto 



The clavicle is proportionally thicker than in Ich. communis ; in the skeleton above 

 cited it is 6 inches 8 lines in length. 



The head is relatively shorter. In the specimen of which the dimensions are above 

 given the mandible is 1 foot 4 inches in length, while in the Ichthyosaurus communis 

 above compared it is 1 foot 5 inches in length. 



In a specimen of Ichthyosaurus latimanus in the Museum of the Philosophical Institu- 

 tion at Bristol I counted 114 vertebrae ; the terminal caudals showed in a greater degree 

 than usual the compressed character indicative of the vertical tegumentary fin. 



Parts of the carbonised integument are preserved on the slab of Lias on which lies 

 the above skeleton ; faint traces of integument lie above and beneath the deflected caudal 

 vertebrae ; a broad patch remains about four inches beyond the last preserved centrum, 

 though not the last of the series. This is the sole direct evidence I have as yet detected 

 of the tegumentary part of the tail-fin. Traces of the abdominal integument appear to 

 be smoother than in the similarly preserved skin figured in Buckland's, ' Bridgewater 

 Treatise.' 



If, as has been suggested (p. 44), the pectoral arch and fin relate to occasional 

 reptation on the sea-shore, it may be inferred, from the partial flattening of the articular 

 surfaces of the vertebral centrums, as well as from their proportions, in the present species, 

 characterised as it, also, is by more massive proportions of the pectoral arch and greater 



