120 FOSSIL REPTILIA OP THE 



The vertical diameter of the base of the rostrum, taken across the middle of the 

 nostril, is but 1 inch 3 lines. The premaxillary is impressed by a longitudinal groove, 

 running about three lines above the alveolar border. 



The teeth are long, slender, slightly recurved ; six or seven may be counted in an 

 extent of two inches of the alveolar groove. The length of the crown of the best preserved 

 is 6 lines, its basal breadth being 1 line. 



In the composition of the mandible the angular element is unusually short; it 

 disappears parallel with the hind border of the orbit. On the other hand, the sur- 

 angular is longer than usual, but its chief character is the continuation of the forwardly- 

 directed nervo-vascular foramen, usually present below the hind border of the orbit, into 

 a groove continued forward, towards the lower border of the ramus, and terminating at 

 a vertical line dropped about a nostril's extent in advance of that opening. A second 

 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. tenuirostris, 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. brachyspondylus in PI. XXXIII, fig. 6. The 

 neural spines of the dorsal vertebras 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. 

 platyodon. The coracoid has a deep anterior emargination, and a shallow posterior one j 

 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 

 pus] led 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. 



