1875.] W. Theobald — On Indian and Burmese Species o/"Tnonyx. 177 



J. ephippium, n. s., PI. V, Figs, a, b, c (shell slightly reduced). 



This species is based on a young specimen forwarded to me dried, from 

 Tenasserim. The head on soaking displayed many yellow spots, something 

 like ' stellatus,' but the profile of the skull is very different from the figure in 

 the Fauna Jiaponica of that species, a copy of which I give for comparison. 

 On the back of the shell was a transverse dark mark (b. fig. V.) like a 

 saddle-shaped flap, not quite symmetrical on both sides. Though a young 

 animal, no traces of ocelli were visible, and the peculiar saddle marking has 

 not been noticed that I can find on any described species. The mark is 

 not visible on the dried shell but becomes distinct on soaking the shell in 

 water, and was no doubt conspicuous during life. Anterior odd bone of the 

 thorax smooth. Disk profusely covered with granular tubercles (each tubercle 

 being rough like a mignonnette seed) ranged in sub-parallel rows. Thorax 

 considerably arched with a prominent vertebral ridge. Sternum very eartili- 

 ginous without any pitted bone whatever. The species approaches ' ornatus' 

 but would seem to be distinguished by its colouration from that species, and 

 from all others with the descriptions of which I am acquainted. Those who 

 may be inclined to question the specific value of colouration in the young of 

 this genus should remember the words of Dr. Gray, who remarks that the 

 " colouring of the young animal forms one of the best characters of the 

 species of the genus" (Sup. Cat. S. R. p. 103). 



Sao. — Tenasserim. 



I have quite failed to arrive at any satisfactory opinion, as to whether 

 any of the species noticed in this paper should be referred to Gray's genus 

 Aspilus — beyond the fact, that if the genus Aspilus really possesses only 

 two linear callosities as stated, then none certainly belong to it that I am 

 acquainted with, but I am inclined to doubt this character, partly from 

 reasons stated before with respect to B. Hamilton's figure of T. gatajlwl, 

 and partly from the youth of so many of Dr. Gray's specimens, and the 

 consequent probability that this character may have been partly due, where 

 observed in some cases, to immaturity. 



There is, however, one character which may be made to serve as the 

 means of dividing this genus into sections, each possessing a fixed geogra- 

 phical range, and that is the character of the mandible, for in all the spe- 

 cies from the eastern coast of the Bay of Bengal, the mandible is traversed 

 inside, in front, by a sharply marked median ridge (r. Plate III), whilst in 

 species from Hindustan, in place of this ridge there is either a smooth sur- 

 face or a depression (f. Plate IV). 



The members of either section may be briefly characterised as follows. 



