324 Eev. T. E. R. Stebbins- on new 



& 



of Neothauma agrees in general structure with that of Vivi- 

 parus. The tentacles certainly are very short and com- 

 pressed^ but tliat is merely of specific value. 



The genus Neothauma was proposed on account of the 

 aperture being somewhat effuse anteriorly and of the broad 

 sinus in the outer lip, and at the time it was conjectured that 

 these characters indicated some corresponding anatomical 

 peculiarities. The right neck-lappet certainly is rather large, 

 and doubtless the object of the labral sinus is to accommodate 

 this siphonal structure. Beyond this there appears to be no 

 reason for separating this form generically from Viviparus. 



There is a species described by Prof. E. von Martens from 

 China — '^Paludi'na (Melantho) auriculata " — which feebly 

 exhibits both an anterior effusion and a lateral emargination, 

 and some of the specimens also have a peripherial angle like 

 Neoihanma [vide Novit. Conch, vol. iv. pi. cxxxv. figs. 4-6). 

 ^^Paludina angvlata^ Lea," a North-American form now placed 

 in the genus Ti/lotoma, has the aperture prolonged at the 

 base, but the outer lip exhibits only a very slight trace of a 

 median sinus. After careful consideration I now regard the 

 extreme development of a labral sinus in Neothauma merely 

 as a specific character, and not of generic importance. It 

 will therefore pass into the synonymy of the genus Viviparus. 



XLIII. — Sessile-eyed Crustaceans. 

 By the Rev. T. R. R. Stebbing, M.A. 



[Plates XY. & XVI.] 



A netv Species o/Talorchestia. 

 Of this widely distributed genus no European species appears 

 to have been hitherto noticed. The name of the genus refers 

 to its close connexion with the genera Talitrus and Orchestia, 

 it being in a manner compounded of both, since the males of 

 Talorcliestia are Orcliestiai^ while the females are Talitri. 

 The distinction of the three genera can therefore only be 

 regarded as conventional ; yet it cannot well be relinquished, 

 on account of the large number of species that have to be 

 dealt with. It is attended by the special inconvenience that 

 in this group animals of which only one sex is known cannot 

 have their genus definitely determined. Thus ^'Orchestia 

 {Talitrus) imgettensis^'' Dana, and '"'' Talorcliestia'i ajricana^'' 

 Sp. Bate, are still uncertain, both having been described from 

 females only. 



