2 Dr. P. P. Carpenter on new Forms of Mollutca 



dm eleaianter variegata ; striis inorementi concentricis, postice ex- 

 tantioribus; umhonibus postice flectentibus, obtusis ; parte antica 

 prolongata, regulariter excurvata ; margiiiibus dorsali et ventrali 

 subparallelis, subrectis ; parte postica curtiore, subangulat'a : intua, 

 dent. card, utraque valva ii. minutis, quorum alter bitidus ; y. 

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

 Curtis, latis, pariim concavis, snbito sectis, valvis postea subalatis ; 

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

 alt. -15. 



Hab. Neeah Bay {Swan) ; Monterey and Catalina 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, Venericardia, and Lucina. It first appears in 

 the Great Oolite, where it is represented by Astarte {Miodon) 

 orbicularis, J. Sby. Min. Conch, pi. 444. f. 2, 3. This must not 

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

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

 Crag-series as Astarte cordis. The following is the only recen>t 

 species at present known. 



9. Miodon prolongatm. 



M. testa parva, solida, tumida, corapacta, 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 expressis, dorsaliter obso- 

 letis, a liris incrementi concentricis, plus niinusve distantibus, ex- 

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

 obsoletim crenulato ; cardine dentibus v. dextr., uno postico, inter 

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

 gular!, post, valde elongato, lat. ant. minimo, obsoleto ; cicatr. add. 

 subrotundatis, ventrahter sitis. Long. "23, lat. "24, alt. -le. 



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



Testa inter Modiolam et Lithophagum intermedia, cylindracea ; 

 umbonibus obtusis ; parte antica longiore ; ligamento subinterno, 

 valde elongato ; epidermide haud testacea. 



Animal byssiferum, in cryptis affixum; musculis 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, fidav, smaller ; ofiovs, tooth. 



236 



