184 Mr. W H. Benson on Indian and Burmese 



tris subtiliter punctatis, subpubescentibus, fuscis ; antennis pedi- 

 busque rufo-flavis. 

 Long. Corp. ^ lin., lat. f lin. 



This minute species varies somewhat in size and also in colour : 

 one example before me is of a deep-black colour, the thorax 

 being somewhat fuscous; this same example is perceptibly 

 smaller in size. In the absence of any series of specimens, I 

 can detect no necessarily permanent difference which would 

 constitute it a distinct species. H, adumbratus is less distinctly 

 punctured than H. Emilianus ; it is, moreover, easily recognized 

 by its manifest pubescence. 



Three examples were taken by M. Truqui in Mexico. In the 

 cabinets of Mr. Fry and the Rev. Hamlet Clark. 



b. Thoracis striola in elytris hand continual a. 

 16. H. apicatus, n. sp. 



H. breviter ovatus, apiee attenuatus, subrotundatus, modice depressus, 

 glaber, punctatus ; capita flavo ; thorace ad basin subtilissime 

 punctato, rufo-flavo aut flavo ; elytris crebre punctatis, rufo- 

 ferrugineis ; pedibus antennisque flavis. 



Long. |-| lin., lat. f lin. 



This pretty minute species resembles in size and coloration 

 H. convexus, Aube ( = Desmopachria nitida, Bab., Trans. Ent. Soc. 

 Lond. iii. p. 16), of Brazil : it is, however, an entirely different 

 species ; the basal strise of the thorax place it in a different sec- 

 tion of the genus ; it is more acuminated at the apex, and not so 

 globose ; the punctation of the elytra is much more distinct than 

 in H. convexus. In form it approaches H. granarius of Aube. 



A single example has been kindly communicated to me by 

 M. Deyrolle of Paris, received by him from "Teapa,^' Mexico. 



XIX. — Descriptions of Indian and Burmese Species of the Genus 

 Unio, Retz. By W. H. Benson, Esq. 



Having collected specimens of the genus Unio in Bengal, Bahar, 

 the Doab, Oude, Bohilkhund, Bundelkhund, and other parts of 

 the Gangetic region, from Calcutta to Delhi and the base of the 

 Himalayan range, and having received others from correspondents 

 who have kindly transmitted the productions of tracts which I 

 had no opportunity of visiting dunng the years of my residence 

 in India, I have procured a series of the species, inhabiting the 

 waters of that country, which no other collector is likely to have 

 had opportunities for obtaining. 



Considering the mode in which the species of this difficult 

 genus approach each other in their variations, I undertake the 



