OF MOLLUSKS FROM MAZATLAN. 27? 



Genus Cycladei la. 



Testa hivalvis, tenuis, (Bquilateralis, aquivalvis, haud hians, itm~ 

 bonibus planatis. Ligamentum tenuissimum, externum. Oardo 

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

 radiantibus. 



56. Cycladella papyracea, n. sp. 



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

 suborbiculari ; eoncentrice fortiter lirata, liris rotundatis, intus 

 excavatis ; tota superjicie hneis granulosis radiantibus creber- 

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

 ffini dorsali subparallelis ; dent. lat. validis. 



= " Tellina teburnea, 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 KelliadeB, although in other respects its affinitieo 

 appear to be with (Edalia and Gooperella. 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. 



JJab. Mazatlan ; one perfect specimen from HaTre Collection 

 {ilus. Hani.') ; fragments, Liverpool Collection, 



706. TMONTACUTA OBTUSA, n, Sp. 



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

 phana seu chalcedonica, haud punctata, leevi ; marginibus ple- 

 rumque regulariter excurvatis, dorsali recto, umbonibus haud 

 prominentibus ; cardine, utraque in valva, dente uno cardinali 

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

 altera vix conspicuis. 



Differs from 1 M. dioneea in the elongation of the lateral teetli, 

 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 trnus 

 parent. 



696. Pectuncultts, sp. ind. 



Tablet 2531 contains a minute valve, -033 across; outside ^'.^ 

 close, prominent concentric ridges, foliated by about twenty-i'cu 

 17 257 



