424 Dr. P. P. Carpenter on new Forms of MoUusca 



tlm eleganter varie^ata ; stviis incrcmenti concentricis, postice ex- 

 tantioribus; umboulbus postice tlectcntibus, obtusis ; parte antica 

 prolongata, regiilariter excurvata ; marginibus dorsali et ventrali 

 subparallelis, subrectis ; parte postica curtiore, subangulata : intus, 

 dent. card, utraque valva ii. niinutis, quorum alter bifidus ; v. 

 dext. dent, lat., ant. curto, satis cxtante, post, nullo ; nymphis 

 Curtis, latis, paruni concavis, subito sectis, valvis postca subalatis ; 

 sinu pallii fere cicatr. aut. tenus porrecto. Long. '72, lat. '42, 

 alt. -15. 



Hab. Nceah Bay {Swan) ; Monterey and Cataliua Island, 

 20-60 fathoms, rare [Cooper). 



Subgenus Miodon*. 



Testa Lucinoidea, dentibus cardinalibus, ut in Cardita, elongatis ; 

 lateral! antico parvo instructa. 



This little group of species is intermediate in character be- 

 tween Astarte, Vcnericardia, and Lucina. It first appears in 

 the Great Oolite, ^Yhere it is represented by Astarte [Miodon) 

 orbicularis, J. Sby. Min, Conch. })1. 114. f. 2, 3, This must not 

 be confounded with a second and true Astarte orbicularis, by the 

 same author, pi. 520. f. 2. It apjjcars in Mr. Searles Wood's 

 Crag-series as Astarte corbis. The following is the only recent 

 species at present known. 



9. Miodon prolongatus. 



M. testa parva, solida, tumida, compacta, albida; ventraliter antice 

 valde prolongata, excurvata ; lunula longa, rectiore, hand impressa ; 

 umbonibus antice inflectis, obtusis, valde prominentibus ; margine 

 dorsali postico parum excurvato ; costis radiantibus x.-xii. latis, 

 obtusis, marginem attingentibus, parum expi'essis, dorsaliter obso- 

 letis, a liris increment! conccntricis, plus minusve distantibus, ex- 

 pressis, hie et illic interruptis : intus, margine a costis plus minusve 

 obsolctim crenulato j cardine dentibus v. dextr., uno postico, inter 

 duas fossas elongato, et lat. ant. lunulari; v. sinistr., dent. ant. trian- 

 gular!, post, valde elongate, lat. ant. minimo, obsolete; cicatr. add. 

 subrotundatis, ventraliter sitis. Long. '23, lat. '24, alt. '16. 



Subgenus Adula, Add. (diagn. auct.). 



Testa inter Modiolam et Lithophagum intermedia, cylindracea ; 

 umbonibus obtusis ; parte antica longiore j ligamento subinterno, 

 valde elongato ; epidermide baud testacea. 



Animal byssiferum, in cryptis affixum ; muscuhs adductoribus 

 majoribus, antico ovato. 



Constituted by Messrs. Adams for A. soleniformis, D'Orb., 

 which very closely resembles the young of the Vancouver species : 

 enlarged to receive the shells of Lithophagoid shape which are 



* Th. fieiav, smaller; odovs, tooth. 



