OF MOLLUSKS FROM MAZATLAN. 



Genus CYCLADEI IA. 



Tata bivalvis, tennis, tzquilateralis, cequivalvis, hand hians, um~ 

 bonibus planatis. Lig amentum tenuissimum, externum. Cardo 

 linea curvata, dent. lat. distantibus, card, transversis, hand 

 radiantibus. 



56. CYCLADELLA PAPYRACEA, n. sp, 



C. t. tenuissima, subdiaphana, epidermide tenui induta, planata t 

 suborbiculari ; concentrice fortiter lirata, liris rotundatis, intus 

 excavatis; tota superjicie hneis granulosis radiantibus creber- 

 rimis minutissime ccelata; dent. card, i.-ii. transversis, mar- 

 gini dorsali subparallelis ; dent. lat. validis. 

 = " Tellina leburnea, Hani." (fragments only), Maz. Cat. no. 56. 

 Mr. Hanley kindly sent for my inspection a perfect pair (as 

 " Lepton "), which he had found nestling in a burrow in Spondylus. 

 The hinge more resembles Cyclas (Lam.) than any other known 

 genus. Its great peculiarity is, that the cardinal teeth, instead of 

 radiating from the umbo, fall in the curve of the hinge-line, as 

 though uniting the lateral teeth. The shell is too thin (being deeply 

 indented within by the concentric waves) to make out the pallial 

 line ; but no trace of sinus is visible. It may therefore rank, provi- 

 sionally, under Kelliadce, although in other respects its affinitiea 

 appear to be with (Edalia and Cooperella. The ligament appears 

 little more than a prolongation of the epidermis. Beside the trans- 

 verse cardinal teeth, there is in each valve a curved line, slightly 

 raised, like the end of a finger-nail, which bounds what would be the 

 lunule in other shells. 



Long. -1, lat. -123, alt. -045. 



Hab. Mazatlan ; one perfect specimen from Havre Collection 

 (Mus. Hani.) ; fragments, Liverpool Collection, 



706. ?MONTACUTA OBTUSA, n. Sp. 



?M. t. planata t valde incequilaterali, subrhomboidea ; subdia- 

 phana sen chalcedonica, hand punctata, Itevi; marginibus pie- 

 rumque regulariter excurvatis, dorsali recto y umbonibus haud 

 prominentibus ; cardine, vtraque in valva, dente uno cardinad 

 et fossa ligamentali ; dent lat. altera valva elongatis t reclis, 

 altera vix conspicuis. 



Differs from ? M . dioneea in the elongation of the lateral teeth, 

 and in the possession of a distinct cardinal tooth in each valve. 



Long. 047, lat. -06, alt. -01. 



Hab. Mazatlan ; two fresh specimens, Liverpool Collection* 



Tablet 2530 contains the larger specimen; the other is trans 

 parent. 



696. PECTUNCULTJS, sp. incu 



Tablet 253 1 contains a minute valve, '033 across ; outside *r*.v 

 close, prominent concentric ridges, foliated by about twenty-frm 

 17 257 



