366 Mr. E. A. Smith on Molhiscafrom the 



part. Tail slightly shorter than the head and body, slender, 

 very thinly clothed with minute brown hairs, whicli are 

 everywhere of the same colour, while the skin of the tail itself 

 is also dark brown above and below for its whole length. 



Skull, as compared to that of P. aztecus, decidedly more 

 lightly built and flatter above when viewed in profile ; muzzle 

 longer and narrower ; supraorbital edges square but not 

 beaded ; palatal foramina widely open ; bullae rather smaller. 



Dimensions of the type (an adult male in spirit) : — 



Head and body 99 millim, ; tail 92 ; hind foot 22 (with 

 claws 23) ; ear 17 x 13'5; heel to front of last foot-pad 10. 



Skull : greatest length 30*5, basal length 25, basilar length 

 to henselion 23*1, greatest breadth 15*4; nasals 12x3*3; 

 interorbital breadth 4"6 ; interparietal 3*7 X 10 ; palate length 

 from henselion 12*4; diastema 8'2 ; palatine foramina 5"8x 

 2-3; upper molar series 4"1. Lower jaw: condyle to incisor- 

 tip 18; coronoid to angle 7*3 ; vertical height ot' ramus below 

 m-l 3"6. 



Hah. Guatemala. Coll. Bernoulli. 



%;e: B.M. 86.5.13.4. 



The only species that I know of related to this peculiar 

 dark-coloured short-tailed Peromyscus are two in the Museum 

 collection from " S. Mexico," Coll. Salle. One is, however, 

 larger and the other smaller than P. gymnotis^ and both have 

 more or less bicolor tails and hairy ears. Tliese two species 

 are, I believe, both undescribed ; but, in view of the fact that 

 their exact locality is not known and that there is reason to 

 hope for a proper American revision of the Mexican Pero- 

 mysci^ based on Mr. Nelson's magnificent collections, I prefer 

 to refrain from describing them. 



XLIV. — Natural History Notes from H.M. Indian Marine 

 Survey Steamer ^ Investigator^^ Commander C. F. Oldham, 

 R.N. — Series II., No. 10. Peport upon some Mollusca 

 dredged in the Bay of Bengal and the Arabian Sea. — 

 Appendix. By Edgae A. Smith. 



Since the publication of the above report in the September 

 number of the * Annals ' I Lave received from Mr. Alcock, the 

 Superintendent of the Indian Museum at Calcutta, two species 

 of Mollusca which have already been figured and briefly 

 described in the earlier accounts of the dredgings of the 

 ' Investigator ' by Messrs. Alcock and Wood-Mason. Of one 

 of the species I have drawn up a detailed description, and of 



