78 BRITISH FOSSIL REPTILES. 



and narrower longitudinal groove extends along the dentary about two lines below the 

 alveolar border. 



The length of the jaws cannot be determined in this or in the typical specimen, 

 their fore end being broken off, but sufficient remains to indicate that Ich. laticeps 

 belonged to the long and slender-jawed species, with small and slender teeth to match ; 

 and associated, as in Ich. temiirostris, with a powerful fore paddle, supported by compa- 

 ratively few and relatively large phalanges. 



The proportion of the longitudinal to the transverse diameter of the vertebral cen- 

 trums is contrasted with those of the Ich. braclipjwndi/his in Tab. XXIX, fig. 6. The 

 neural spines of the dorsal vertebrae are relatively short and with distinct intervals. 

 Thirty-eight are preserved between the scapula and ilium. 



The scapula is characterised by the greater relative expanse of its articular end in 

 comparison with the breadth of the body, resembling in this respect that of Ich. 

 2)lafyodon. The coracoid has a deep anterior emargination, and a shallow posterior one ; 

 the antero-posterior breadth of this bone is 4 inches, the transverse extent is 3 inches. 

 The left coracoid, with the corresponding humerus and a few paddle-bones, have been 

 puslied dextrad and appear beneath the right coracoid, from which the corresponding 

 paddle has been removed. 



The pelvic bones of the right side are well shown. The ilium, 2 inches 4 lines in 

 length, is directed obliquely backward and downward ; its upper end is one inch in 

 breadth. The pubis, 2 inches 3 lines in length, has a distal breadth of 11 lines ; its 

 fore border is almost straight. The ischium, 2 inches in length, has a distal breadth of 

 1 inch 3 lines. The margin towards the pubis is more concave than the opposed one of 

 the latter bone. The hind border of the ischium is moderately concave. 



Compared with the same bones in Ichthyosaurus communis the pelvic elements are 

 more robust. 



Of the structure of the appendage of the pectoral and pelvic arches, or fins, I have 

 not. as yet, obtained satisfactory evidence. 



The fossils which have served in the present section of the Chapter have been 

 obtained from the Lias of Lyme Regis and Charmouth. 



h. Ichthyosaurus acutirostris,^ Oio. Tab. XXIV, fig. 2. 



This species is so named from the slender, sharp-pointed form of the snout, unaccom- 

 panied by such proportions of length as characterise the Ichthyosaurus tenuirostris and 

 Ich. lonyirostris (ib., fig. 3). 



1 'Report,' ut supra, p. 116. 



