208 REPORTS ox THE STATE OF SriEXCE. 



broad and depressed, but the phalangeal formula is clearly 2, 3, 4, 5, 4, as 

 in Splienodon. Metatarsal I, is remarkably short and broad, and the 

 extremity of its toe scarcely reaches beyond the distal end of the 

 metatarsal of the next toe, being shorter than in the existing genus. 

 Metatarsal IV. is much the lai'gest, l)ut its length equals only half tliat of 

 the fibula, whereas in Splienodon the same bone is nearly two-thirds as? 

 long as the fibula. Metatarsal V. is curiously modified and displaced 

 upwards, as in Splienodon and the Laccrtilia ; but the distal end of its 

 toe only reaches just beyond the distal end of metatarsal IV., whereas 

 the corresponding toe oi S2'>lienodon reaches the end of the first phalangeal 

 of toe IV. 



Plastron.— 'The plastron of abdominal ribs is at least as extensive as, 

 in Sphenodon, and its shape seems to indicate that the body was rela- 

 tively broader in Blajnchosanrus than in this existing genus. The 

 abdominal ribs are very slender, arranged in three longitudinal series, 

 and well seen both in B.M. No. R. 1238 and S. No. 5. The anterior rows 

 just behind the pectoral arch are not thicker than the others, but their 

 middle piece is sharply lient, so that its two arms are inclined to each 

 other in the median line at about a right angle (Plate II., fig. 4). This 

 angulation gradually disappears in the middle pieces of the hinder abdo- 

 minal ribs, which are only gently arched (Plate II., fig. 5). 



SM71. — The dermal covering of Rhynchosaurus has already been noticed 

 by Burckhardt (5) and the present writer (6), and is especially well shown 

 on part of the fore limb represented in Plate II., fig. 2. It is indicated 

 in the fossils merely by an impression, without any trace of calcified 

 matter ; and it is most probably to be interpreted as an armature of 

 horny scales. It is seen in the fossils in the region of the ribs, below 

 the root of the tail, and on the fore limb, so probably covered the whole 

 animal. The scales are very small and irregularly rhombic or polygonal 

 in shape, each with a slightly elevated central boss. In one specimen 

 F>urckhardt interpi-ets the markings to mean tiiat on the hinder part of 

 the back the scales are much larger and flatter than tliose of the flank • 

 Imt this determination is somewhat uncertain. 



Conclusion. — The general result of these new observations on lihyn- 

 rhosau7-iis is to confirm previous statements as to the resemblances and 

 differences between this Triassic reptile and the existing Splietwdon. It is 

 obviously a typical Rhynchocephalian, and is more specialised in several 

 respects than its surviving representative. It resembles many \ery ancient 

 reptiles, however, in the relatively great expansion of its ossified coracoids 

 and pubes, and in the .small size of the obturator foramen in the pelvis. 

 It also appears to be noteworthy for the relatively small space available 

 for a cartilaginous sternum. The condition of the pectoral and pelvic 

 arches, however, may have been partly correlated with an aquatic mode of 

 life ; for there cannot be much doubt that lihynchosaurus was more 

 amphibious in habit than Sjyhenodon. The eveitcd rims to (he upturned 

 eyes, the sigmoidally bent femur, and the broad flattened phalanges of the 

 hind foot all suggest life in water. 



TAferature. 



1. R. Owen,— ' Description of m\ Extinct Lacortian Reptile, Rliynchosaima 

 irrticeps, Owen, of which (he bones and foot-prints cliar.acterise the Upper New Red 

 Sandstone .it Grinsill, near Shrewsbury,' ' Trans, t'amb. Phil. Sop.' vpl. vii. (1342^ 

 pp. 355-369, pis. v, vi. 



