MUSEUM OF COMPARATIVE ZOOLOGY. 13 



Mr. Jeffreys, F. Ii. S., on the British Deep-Sea Dredging Expedition, 

 which was presented by him to M. de Pourtales.* The W.Jlorblana j)re- 

 sents very little variation among specimens of similar ages. A compar- 

 ative diagnosis is here given. 



W.floridana. — Color grayish or brownish white. Form nearly an equi- 

 lateral triangle, widest near the anterior edge ; much inflated. Anterior 

 margin very strongly flexuous, the concavity being in the haemal (dorsal) 

 valve. The anterior corners of the haemal valve sharply pointed. Area 

 very narrow and short, deltidia just completing the foramen. Sides almost 

 flat, neural (ventral) valve broadly channelled in the middle. Apex 

 but slightly produced, short, rather acute. Cardinal process minute, 

 pointed, not recurved. Hinge plate wider than long ; anterior point over 

 the septum, behind the crura of the apophyses. Hinge teeth very short 

 and slender. Anterior ends of the lateral loops of the apophyses broadly 

 flaring, the shelly portion of these loops broadest near their ends ; hamial 

 arms of the apophyses close together and parallel for half the length of the 

 shell. Narrowest part of the recurved loop near its posterior end. Visceral 

 area small, muscular impressions within the posterior third of the dorsal 

 valve. Stomach spherical with a long cylindrical intestine. 



W. septigera. — Color as in the last. Form roundly ovate, somewhat 

 truncated and wider in front. Anterior margin more or less flexuous. 

 Anterior corners of the haemal valve obtusely rounded. Area much wider 

 and longer, solid, with no median line indicating a separation or division 

 into deltidial plates. Sides rounded, inflated. • Neural valve not chan- 

 nelled, slightly concave near the exuosity flat the anterior margin. Apex 

 somewhat produced, blunt. Cardinal process broad, blunt, short, hardly 

 differentiated from the hinge plate. Hinge plate longer than wide, ante- 

 rior point passing forward between the crura. Hinge teeth very stout and 

 strong. Anterior ends of the lateral loops incurved, their laminae widest 

 near their posterior portion. Haemal arms of the apophyses diverging in 

 a wide curve from the hinge plate. Recurved part of the loop short, sides 

 nearly parallel. Visceral area very small, muscular attachments even 

 more posterior than in the last. Stomach posteriorly produced into a 

 point, without differentiation of the intestine, and very much shorter than 

 in the last. 



W. liaphaelis. — Color deep brown. Form rather elongate, squarish, 

 widest near the middle. Anterior margin sharply, shortly flexed. The 



* I have since had the opportunity, through the kindness of Mr. Jeffreys, of examin- 

 ing other and more normal forms of this and several other species obtained by him. 

 These included one specimen of the septigera, which he regarded as a transition toward 

 W. fioridana, which has been figured for the Zoological Society, and which he very 

 politely lent for comparison. It is elsewhere referred to. 



