2 Dr. P. P. Carpenter on neir Forms of MoUusca 



tim elesantcr variesata ; striis iiirrcmenti conrentricis, postlce ex- 

 tantiorihus ; iimhoiiibus postice flectcntibus, obtusis : ])arte antica 

 prolongafa, regulariter exeiirvata ; niargiiiibus dorsali et ventrali 

 subparallelis, subrt'ctis ; parte posticn curtiore, subaiigiilata : intus, 

 dent. card, utraque valva ii. miiiirtis, quorum alter bitidus ; v. 

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

 Curtis, latis, parum concavis, subito sectis, vah is postca subalatis ; 

 sinu pallii fere cicatr. aut. tcuus porrecto. Long. •J'l, lat. •42, 

 alt. -15. 



Hah. Neeah Bay (Siran) ; Monterey and Catalina Island, 

 20-60 fathoms, rare [Cooper). 



Subgenus ]\Iiodon*. 



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

 laterali aiuico parvo instructa. 



This little group of species is intermediate in cliaraetcr be- 

 tween Astarte, Venericardiu, and Liicina. It tirst apjx'ars 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 corbis. The following is the only receuJb 

 species at present known. 



9. ^liodun prnlungutus. 



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

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

 umbonibus antice inflectis, obtusis, valde proniinentibus ; niargine 

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

 obtusis, niarginem attingentibns, parum expressis, dorsaliter obso- 

 letis, a liris incrementi coneentricis, plus minusve distantibus, ex- 

 pressis. hie et illic interruptis : intus, niargine a costis plus miimsve 

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

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

 gulari, po?t. valde elongato, lat. ant. minimo, obsoleto; cicatr. add. 

 subrotundatis, ventraliter sitis. Long. '23, lat. "24, alt. 'IG. 



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



Testa inter Modiolam et Lithophagum. intermedia, cylindracea ; 

 umbonibus obtusis ; parte antica longiore ; ligamento subinterno, 

 valde elongato ; epidermide hand testacea. 



Animal byssiferum, in cry[ttis aftixum ; 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 arc 



* TA. /zeioji', smaller; ofioiis, tooth. 



236 



