r April 5, 1900] 



NATURE 



535 



■the preservation of the cartilaginous sternum, sternal 



and coracoids, and laryngo-tracheal supports. Of 



cervical vertebrae there were indubitably seven, and 



lesser parts of these are so well preserved that the 



thor is able to give a detailed account of the " atlas 

 iplex" and individual relationships of the " inter- 



itra," admitting of comparison with the corresponding 

 parts of recent reptiles. But one sacral vertebra is 

 present, and of the twenty-two so-called " dorsals " ten 

 are proved to have entered into the composition of 

 the sternum. The limbs are of the usual Mosasaurian 

 type, except for a broadening and shortening of the 

 fifth metapodial in both fore and hind members ; 

 while the phalanges of the fourth and fifth digits of^e 

 manus are estimated as nine in number. The catj<ial 

 vertebrae come in for consideration, and there is given a 

 restoration of the entire skeleton in outline, and an ac- 

 companying attempt at that of the animal in the flesh. 

 For this the author expresses his indebtedness to Mr. C. 

 Knight, who, on the whole, does not seem to have been 

 so successful as with some of his earlier efforts of the 

 .kind. The introduction of a " nuchal fringe " by analogy 

 to Platecarpus is risky, and the contour of head and jaws 

 grotesque, if not erroneous. 



Concerning the affinities of the Mosasaurs, the author 

 is unable to decide ; for while showing them to be 

 possessed of varanoid characters beyond those already 

 recognised, he points to differences between the two 

 groups, which he considers irreconcilable with the view 

 that they sprang from a common stem. Here, however, 

 he does not appear to have sufficiently considered the 

 Dolichosaurian kinship, so strongly urged by Boulenger, 

 supported by DoUo, and accepted by Smith Woodward ; 

 and his assertion that the presence of but seven cervical 

 vertebra; is against this is unfortunate, since there is 

 reason to believe that in some members of that suborder 

 the number was thus small. The great expansion 

 and non-fenestration of the unossified portion of the 

 coracoid is a feature in respect to which this Tylosaurus 

 is on a closer structural equality with the Rhyncho- 

 cephalia than with the higher Lacertilia ; and if it be 

 that the bone claimed by Baur as the quadrato-jugal in 

 Platecarpus really represents that, in consideration of 

 the condition and inter-relationships of the palatines, 

 pterygoids, and vomers, so well known in certain Mosa- 

 saurs, there can be little doubt that these struck off from 

 some reptilian type intermediate between the Rhyncho- 

 cephalia and the higher Lacertilia as to-day represented, 

 />. that they arose " at an early stage in the evolution 

 of the Squamata, before the modern Lacertilia and 

 Ophidia had become differentiated," as Smith Woodward 

 has so aptly remarked. Our greatest desideratum in 

 the osteology of these creatures is a fuller knowledge 

 of the posterior portion of their maxillo-jugaljarcade, and 

 it is unfortunate that with the present specimen, in which 

 the conditions for preservation have been so favourable, 

 that has been crushed. 



Diplodocus is a notorious member of the Jurassic 



quadrupedal Dinosaurs, believed to have been an aquatic 



vegetable feeder ; and, as already remarked, a full ac- 



• quaintance with its axial skeleton has been a desideratum. 



The present specimen was obtained from the Como Bluffs 



NO. 1588, VOL. 61] 



of Wyoming, by a prospecting party led by the author 

 in 1897. Hopes of the recover^ of the entire skeleton 

 proved false, but there were obtained a complete set of 

 caudal vertebrie, together with the greater portion of 

 the sacrum, hip-girdle and femur, all in an undisturbed 

 state, and also fragments of the rest of the vertebral 

 column and the ribs. Passing over important details 

 concerning the cervical and so-called " dorsal " and 

 pre-sacral vertebras, with which the memoir deals in 

 detail, it is as concerning the posterior of the latter, 

 together with the sacral and caudal, and the ilium, that 

 interest is greatest. The overlapping, by forward ex- 

 tension of the ilium, of certain free lumbar ribs with 

 accompanying co-ossification of parts furnishes an in- 

 teresting feature of convergence towards the Ratite bird 

 type. Passing on, the author remarks that Diplodocus 

 "gives us a new . . . conception of the Cetiosaurs," as 

 involving the following interesting facts. He points 

 out that the tail — some thirty feet in length — constitutes 

 one-half of that of the whole animal, that the sacral 

 spines mark the highest point in the backbone, and 

 that the sacrum and ilium "come as a centre of power 

 and motion" — the whole set of parts being so disposed 

 as to lead us to regard the tail (which undoubtedly 

 served as a propeller) as a " lever to balance the 

 weight of the dorsal vertebrae " and the anterior 

 portion of the body. He further points to a "balance 

 between the opisthocoelous pre-sacrals and the procoelous 

 post-sacrals," and draws the conclusion that the domin- 

 ating principle of this great backbone is " maximum 

 strength with minimum weight," while (to him) the whole 

 is a mechanical triumph of great size, lightness and 

 strength, which "baffles the Lamarckian as well as the 

 Darwinian." 



Beyond the more salient features above recapitulated, 

 these memoirs are a storehouse of carefully recorded 

 detail, of immense service for reference. Of the illus- 

 trations, no praise can be too high. There are eight 

 plates, of which three are devoted to the Mosasaur, five 

 to the Dinosaur ; and all, with the exception of the 

 third, which is an enlarged copy of a restoration of the 

 skeleton incorporated in the text, are photographs of 

 great merit. In addition, there are twenty-eight text 

 illustrations, which, so far as they delineate parts of the 

 actual remains, are ideal. 



In conclusion, a word or two as to terminology and a 

 looseness of expression, which we regret. In describing 

 the unossified remnant of the coracoid as an " epicoracoid 

 cartilage," and (using the term in its noun form) as an 

 "epicoracoid" on one and the same page, the author 

 is perpetuating a prevailing error against which we 

 have more than once protested. The term "epicora- 

 coid" is only applicable when a distinctly segmented 

 element is present. Unfortunate, again, is the use of the 

 term (p. i8i) " sterno-coracoid plate." The sternum, 

 which is apparently meant, is compared with that of 

 certain living lizards ; but when of these it is found that 

 while at most three pairs of ribs contribute to its form- 

 ation, in two of the species a second sternal cartilage is 

 present, the comparison of Tylosaurus, with its ten pairs 

 of costal ribs, is at least strained. Indeed, in its elon- 

 gation and apparent longitudinal cleavage— its two most 

 distinctive characters— the sternum of this aquatic reptile 



