PLATE IV I. 



Leg'encl. jm. Posteiior acUiuctors. 

 aa. Anterior ail(iuctoi's. 

 (111. Dorsal adjustoi-s. 

 va. Ventral ailju.stors. 

 mm. Mesenten(^ niiisciilar imiiression. 



|i. I'arietal imiii'e.ssion. 



m Median impressions. 



Ii. Hracliial nni.scnlar im])re.ssion. 



V. Va.scular trunks, 



v'. Viusciil;ir lirani'lies. 



CKANIKLLA, (Ehi.iout. 

 Craniella Uluichi, sp. IIOV. 



Vig. I . A cast ol the interior of a losvei" valve, somewhat restored on ttie rig-ht side ; showing' the strong 

 antei'i. r and very obscure posterior adductor impressions, and the marks of the vascular sin- 

 uses. The sliell is convex an<l .shows no evidence of attachment, thougli the external sui'face is 

 overgrown with a bryozoan. Di'awn from a gutta-percha cast of a natural interior. X 1.5. 

 Ti-enton limestone. Minneapolis, M'mnesotn. 



Fig. 2. The niternal cast of an upper valve, believed to be of the same sjjecies. The sigmoid vascular 

 impressions ai-e simiilei- tVian elsewhere observed ; the scars of the ilorsal adjustors and of 

 muscles accessory to the anterior adductors (possibly the brachial muscles) are also apparent. 

 Drawn from a gutta-percha cast of a natural interioi-. X l.o. 

 Trenton limestone. MimuapoUs, Minnesota. 



CUAXIELLA Hamiltoni.e, Hall. 



Fig. 3. The interior of a lower valve attached to a Stkkftei.asim.^ ; showing the usual character of the 

 muscular scars, viz , anterior and posterior adductors, the venti'al adjustors, and post-median 

 or mesenteric impression ; also the characteiistic radiating vascular sinu.scs. 

 Hamilton group. Cimandaigua Lake, N. Y. 

 4. Tlie interior of an upper valve. 



Falls of the Ohio. 



Fi'om Pala>ontology of New York, vol. iv, ]il. iii, tig. 23, 



Fis 



Fi(j 



vascular impressions, and very 

 attachment to an individual of 



7(;, Kg. 3. 18(50. 



Corniferous limestone. 

 The interior of an attached valve. 



Three indix-idiials of ilift'erent sizes, attached to the sui-face of Tropi/jAih-ptu-s- carlnatus. Opero 

 citato, pi. iii, tig. 19. 



Hamilton group. ]Ve.^tern iVtic Yor/i. 

 The interior of a lower valve; showing the usual muscular and 



great thickening of the shell. X 2. 

 An upper valve ; showing the modification of the surface from 



iSpirifcr audaculii.-:. 

 Profile view of a normal .shell, attached to Tinpidoleptus carinatus. 



Hamilton group. Caiiandoigua Lake. N. Y. 

 The exterior of an upper valve. From Thirteenth Rept. State Cab. Nat. Hist., p 



Hamilton group. We.iteni New York. 

 Au upper valve, modified by attachment to the post^lateral portion of aright \a.\\f. o( C'ypriciinlcllo 

 (Microdfin) hellistriala. 



Hamilton group. Canaudaiyua Lake, N. Y. 

 An individual greatly modified by attachment to Tropidoleptun carinatiis. 



An internal cast of a large uiijter valve; .showing the usual nuiscular seal's and Ihe pecMiliar 

 sigmoid vasi'ular trunks with their ramifications. 

 Hamilton group. Pratt's Falls, N. Y. 

 An internal cast of a very convex upper valve, greatly modified by attachment. X 2. 



Hamilton group. Canandaigna Lake, iV. i'. 

 Au internal cast of an ujiper valve; showing the characteiistic impressions. X 2. 



Hamilton group. Bellona, N. Y. 

 An internal cast of a convex and apparently free lower valve ; showing the closer apiu'oximation 

 of the anterior and posterior adductor scars than in the opposite valve, the lieep impresssion of 

 the mesenteric niu.scle, and the radiating vascular sinuses. The figure is slightly I'estored on 

 the left side. X 2. 



Hamilton group. Center-field, N. Y. 



I'lIOLIDOPS, Hall. 

 Pholidoi'S Tkknionkn.sis, II:i11. 



17. A slightly crushed specimen. X 4. 



Trenton limestone. MiddleviUe, N. Y. 



PhOLIUOI'S ClNCINNATEN'SIS, Ililll. 

 Fig. 18. The exterim* of a iioi-mal specimen. X 4. 



Hudson River gi'ou|i. Ciiicinuali, Ohio. 



