MONOGRAPH OF THE GENUS 

 DONAX, Linnmis. 



Char. Gen. Testa aequivalvis, ineequilateralis, subtrigona, bi- 

 mnsculosa, postice plus minusve truncata; pallii impressione late 

 amentata. ; hgamento externo ; dentibus cardinalibus in valva dex- 

 tra duobus, in valva sinistra uno ; dentibus lateralibas duobus, 

 approximatis vel uno remote 



A large sinus in tbe impression of the mantle, and the absence 

 of a cartilaginous pit, will be sufficient to distinguish the shells of 

 this genus from the few others with which they might otherwise 

 possibly be confounded. 



Species. 



1. scortum (f. 1, •!, ;3), Linn. — Testa tumida, subeequilaterali, 

 striis radiatis et liris concentricis decussata, extus alba seu pallide 

 fulva, violaceo conceutrice fasciata, intus violacea, antice subacu- 

 minata, laminis laqueatis subdistantibus limbriata, postice acute 

 arcuatim angulata, ad angulum spinifera, area postangulari con- 

 cava, acuminata, decussata. — Specimens differ in the degree of 

 development of the spines and fringes; and we have in our hands 

 a specimen from Mr. Taylor's collection which is white, and has 

 the posterior angle produced remarkably. 



2. Carinatus (f. 4, 5), ZZa«£— Testa tumida, lata, polita, cas- 

 taueo-violacea, radiatim iinpresso-striata, striis antice evanidis, 

 umbonibus elevatis, angulo postico subcarinato, area postangulari 

 arcuatim declivi, coucava, striata, infra producta, acuminata, latere 

 antico declivi, ad terminum acuminate — Nearest m form to D. 

 scortum, but a polished shell. 



3. acuticarixatus (f. 6, 7), Sowh. — Testa D. carinata simili, 

 baud tantum elevata, carina validiore, area? posticae striis radian- 

 tibus granulatis. — Besides the greater distinctness of the keel, 

 the sculpture of the posterior area distinguishes this species from 

 D. carinata, the radiating stria 1 being close, and crossed by con- 



