Mr. W, H, Benson on new Helicidse. 387 



eleven, the first short rudimentary ray being a true ray, and 

 present in the Uving and extinct species. Troschel has rightly 

 marked it ; but he has mistaken it for a part of the first thick 

 ray, so that this appeared to have two metatarsal bones, one at 

 the side of the other. The fossil fish differs from Tinea in 

 having the dorsal fin decidedly more advanced towards the head, 

 and the caudal fin forked; but if we consider, on the other 

 hand, the thickness of the rays in general and the small size of 

 the scales (also expressly mentioned by Prof. Troschel), we are 

 nevertheless obliged to acknowledge its close affinity to the 

 recent genus*. 



This sexual difference in the Tench appears to be in connexion 

 with the propagation. In the season of spawning I usually 

 found the base of the ventrals, in old males, inflamed, and even 

 excoriated and bleeding. At that time of the year they &re 

 compelled continually to rub the belly upon places w^here the 

 spawn is deposited by the females ; and they are so passionate, 

 that they continue to do so, even if caught, on the bottom of 

 the vessel in which they are kept. 



XXXIX. — New Hehcidse collected hy W. Theobald, Esq., jun., in 

 Burmah and the Khasia Hills, and described hy W. H. Ben- 

 son, Esq. 



1. Helix AcriSj nobis, n. s. 



Testa anguste umbilicata, elevato-conica, trochiformi, oblique stri- 

 atula, obsolete granulosa, subtus minutissime spiraliter striata, 



, albida ; spira elongato-conica, lateribus planis, apice obtusiuseulo; 

 sutura leviter impressa ; anfractibus 6^ planulatis, ultimo vix de- 

 scendente, ad peripheriam acute carinato, basi planiusculo ; aper- 

 tura valde obliqua, tetragono-lunata, peristomate superne expan- 

 siusculo, subtus expanso, reflexiusculo, margine columellari late 

 angulato-reflexo, umbilicum partim celante. 



Diam. major 10, minor 9, axis 9 mill. 



Habitat ad Teria Ghat montium Khasise, raro. 



It approaches the larger H. Capitium, B., of the hill region 

 south of the Gangetic angle ; but, besides the absence of the pe- 

 cuUar colouring of that species, it is distinguished by its more 

 elongate and regular conical form and by the flatter base. The 

 single specimen examined is much weathered, so that the sculp- 

 ture and colour may eventually require an amended description. 

 There is a faint rufous tint, not to be detected elsewhere, towards 

 the termination of the keel. The spire is more attenuate than 



: * Specimens of Tarsichthys elegans from the same locality (Siebenge- 

 birge), in the British Museum Collection, and specimens collected by my- 

 self at that place, exactly agree with Prof. Troschel's description and figure. 



25* 



