116 FOSSIL REPTILIA OF THE 



A dental characteristic of the present species is that which suggested to Conybeare 

 the name platyodon ; the smooth enamelled crown (PI. XXIV, figs. 4, 4') being subcom- 

 pressed, sharp-edged, and pointed ; the longitudinal grooves of the tumid cement-clad 

 root are soon lost upon the coronal base. I have counted 45 — 45 of these teeth in an 

 upper jaw, and 40 — 40 in a lower jaw, and have noted that the crowns are more often 

 snapped off than in the smaller species, which may be indicative of the greater violence 

 with which they have been used. 



From the occiput to the iliac bones there are forty-five vertebrae ; thence to near the 

 end of the tail may be counted seventy -five vertebras ; the total number in the skeleton 

 probably somewhat exceeded 120. One of these vertebrae, from the hinder half of the 

 abdomen, is figured (in the inverted position with the neural surface downwards) in 

 Home's Memoir of 1816. 1 The neural spines are thicker, shorter, and more rounded 

 superiorly than in Ich. intermedins or Ich. communis. The zygapophyses, especially the 

 anterior ones, are well developed, and the vertebras of the trunk and basal moiety of the tail 

 are strongly interlocked, though admitting some inflection. The ribs increase in length 

 to the twenty-fifth pair; at the thirtieth pair they begin to shorten gradually, and, after 

 the fortieth pair, more suddenly, becoming nearly straight at the forty-fourth pair. 

 Thence they are continued like long transverse processes articulated by a simple head to 

 the single di-parapophysis, as far as the hundredth vertebra. 



The scapula (PI. XXXI, fig. 3, 5i) has a relatively broader humeral end than usual. 

 It is preserved with the corresponding clavicle (ib., 58) in a portion of a huge skeleton of 

 the present species in the British Museum. 



The coracoid has a relatively larger or longer scapulo-humeral surface than in Ich. 

 intermedius, and has a narrower and deeper anterior notch or emargination than in Ich. 

 communis; the ento-sternal margin is rather thicker than usual. I have noted a 

 specimen of this bone from Lyme Regis, of which the long diameter was 8 inches 4 

 lines, the short diameter 6 inches. 2 



The humerus is notable for its breadth, especially distally, compared with its length- 

 The proximal rounded end, or ' head,' is tuberculate at its circumference, indicative of 

 powerful ligamentous attachments to the scapulo-coracoid joint. The fore margin is 

 more concave than usual. This latter character is still more marked in the radius, which, 

 with the ulna, presents the generic shortness and flatness, with a slight excess of breadth, 

 as compared with most other species. The anterior emargination is present also in the 

 radio-carpal bone (PI. XXXI, fig. 1, 54), and in the corresponding one in the following 

 series. The next ossicle presents the common pentagonal form. Not more than three 

 series of digital bones are preserved in the subject of figure 1, PI. XXXI. A few 

 supplemental ossicles are preserved at the radial border beyond the middle of the fin- 

 framework. I have not found evidence of a greater number of pectoral digits in any 



1 ' Phil. Trans.,' mdcccxvi, pi. xiv. 



2 ' Report,' ut supra, 1839, p. 114. 



