M. Deshayes' Monograph of Dentalium. 183 



8. D. Dentalts, Linn. D. testd tereti, subarcuatd, costellatd, ruhrd ; 

 costellis octodenis aut viginti ; alternis minoribus. 



Var. a. Testd majore, costis majoribus planulaiis. 



Var. b. Testd duodecim ad sexdecim costatd. 



D. attenuatum. Say, Journ. Acad. Phil, iv, p. 154, pi. 8, f. 3. 



Habitat in mari Mediterraneo. 



Foss. a. in agro Pedemontano ; b, in Marylandia. 



Shell red, curved, subulated, with eighteen or twenty closely set, regu- 

 lar, prominent, rounded ribs, between each of which is a smaller one. 

 Ribs usually continued from the apex to the base, occasionally diminish- 

 ing insensibly, and disappearing towards the opening. Apex acute, sub- 

 ulate, with a very small hole. Opening rounded, rather oblique, its 

 margins very thin and cutting. 



Length 2 inches. Diameter at the base, 2 lines. 



9. D. SULCATUM, Lam. D. testd stibarcuatd, subulatd, costatd ; costis 

 regularibus, continuis, sexdecim. 



Foss. apud Grignon, &c. 



Resembles D. Dentalis in the disposition of the ribs, but differs from 

 it in their number, as well as in size and curve. It is small, pointed, 

 slightly curved, elegantly and regularly covered with sixteen obtuse ribs, 

 continued from the apex to the base, (not varying from twelve to fifteen, 

 as stated by Lamarck, who confounded other species with the present) ; 

 in the anterior half a slight stria is visible between each rib. Opening 

 very thin, cutting, festooned by the termination of the ribs. 



Length 



10. D. FOSSiLE, Linn. D. testd vix arcuatd, longitudinaliter striata : 

 crebris striis regularibus, obtusis, cequalibvs. 



D. costatum ? Sowerby, Min. Conch, pi. 70, f. 8. 

 Foss. apud Siennam et Lauretum. 



Size middling, slightly curved, broader at the base than D. Dentalis, 

 and less acuminated at the apex. Apex smooth ; striee commencing in- 

 sensibly a little above it, and increasing in size towards the opening, nu- 

 merous, closely set, rounded, separated only by a narrow groove. A few 

 transverse striae indicate the growth. 



Length 1 inch 9 lines. Diameter at the base more than 2 lines. 



