R. Lydeliher — Neio Speciea of Merycopotamus. 545 



here noticed. We are unable to refer any cephalothoras as belonging 

 to this form of pygidium, and can only therefore note its occurrence. 



Pygidium one-fourth broader than long, axis one-third the entire 

 breadth, consisting of seventeen coalesced segments which diminish 

 rapidly in breadth to the extremity, which is bluntly rounded, and 

 less than one-third the breadth of the axis at the proximal end ; axal 

 furrows deeply marked. Pleurae thirteen in number, terminating 

 abruptly within the margin, which is finely striated ; neither axis 

 nor pleurae have any ornamentation upon them. 



This pygidium agrees most nearly with the preceding spe^'ies, 

 from which, however, it differs in possessing a greater number of 

 coalesced somites, a character which seems sufficient to justify its 

 separation. 



Formation and locality the same as that of the preceding speciasS. 



Specimens of this species are preserved in the British Museum 

 (Natural History). 



III. — Note on a New Species of Merycopotamus. 



By E. Lydekker, B.A., F.G.S., F.Z.S. 

 Merycopotamus nanus, n. sp. nobis (ex Falc. MS.). 



IN plates Ixii. Ixvii. Ixviii. of part 7 of the "Fauna Antiqua 

 Sivalensis " (1847) ^ a large number of remains of Merycopotamus 

 (nearly all of which are in the collection of the British Museum) 

 are figured under the name of M. dissimilis, although some of them 

 are distinguished as var. major and others as var. minor ; and it thus 

 appears that at that date the authors of the work quoted referred all 

 the remains to one species. It is stated, however, in Falconer's 

 " Pala3ontological Memoirs," voL ii. p. 407, note 4, that in 1846 

 Falconer considered that there were two species, which he proposed 

 to call M. dissimilis and M. nanus ; and some of the smaller specimens 

 figiu'ed in the " F. A. S." under the former name, bear upon them 

 the latter name in Falconer's handwriting. In some manuscript 

 notes of Falconer's, written at a much later date,- the name M. nanus 

 is once again employed (although the tooth to which it was applied 

 does not belong to Merycopotamus at all) ; ^ and it would therefore 

 seem that Falconer had by that time reverted to his original view. 



In the " Pala30utologia Indica " * I, perhaps somewhat incautiously, 

 accepted Falconer's references of all the British Museum specimens 

 to a single species, and observed that the smaller species mentioned 

 by him could not be identified. A recent comparison of all the 

 British Museum specimens has, however, shown pretty conclusively 

 that they belong to two species. 



The cranium and mandible represented in the "F. A. S." pi. Ixvii. 

 figs. 1 and 4, may be regarded as the type of M. dissimilis. The 



1 This is generally quoted as the authority for the genus ; the name occurs, how- 

 ever (with a figiu-e and description), in Owen's " Odontography," p. 566 (1840-45). 

 '^ " Palseontogical Memoirs," vol. i. p. 416. 

 3 Vide " Palseontologia Indica," ser. 10, vol. i. p. 62. 

 * Ser. 10, vol. ii. p. 164. 



DECADE III. VOL. I. —NO. XII. 35 



