OF CONCHOLOGY. 29 



and anterior end, measures — length 1-8 in. ; probable total 

 length a little over three inches ; probable length of aperture 

 2*2 in. ; width of body whorl 1'2 in. ; width of aperture '6 in. 



From the casts and impressions, I am satisfied that the shell 

 has had no other surface markings except the plain, rounded, 

 longitudinal ribs, in which character it resembles P^. indurata, 

 Con., found in the Miocene and Pliocene of Oregon and Cali- 

 fornia. It differs from that species in having more ribs, in their 

 being straighter, and in the tips of the whorls being regularly 

 sloping. In the North American species I could never succeed 

 in uncovering the columella sufficiently to satisfy myself of the 

 presence of the characteristic plaits. In the present shell I have 

 detached traces of two, if not three, and now suspect that they 

 will eventually be also found in the other. 



All the specimens of this species are from a hard, yellowish 

 claystone, containing Pholas Chilensis, Molina, and the Thracia, 

 described below. No other species of this paper appear to have 

 come from the same rock. 



TURRITELLA, Lam. 

 T. COCHLEIFORMIS, Gabb. 



Shell elongate, slender ; whorls numerous ; concave and slop- 

 ing above and bearing a little below the middle, two sharp, 

 strongly elevated revolving ribs with a concave interspace ; below 

 these is a third rib, less prominent and separated by the same 

 distance as that between the others. On the last volution it 

 forms a part of the base, while on the upper whorls it unites 

 with the upper margin of the succeeding whorl, placing the 

 suture a little above the middle of a regular concave space. 

 Aperture sub-quadrate, base slightly convex and having but the 

 one rib mentioned above. 



Numerous fragments of this species are associated with the 

 Fusus, Tritoniiwi, and Littoj'ina. It is closely allied to T. 

 cochlea, Rve., Icon. Conch., Sp. 29, but differs in the two caringe 

 being close together, and in having but one rib on the base in- 

 stead of the two in Reeve's shell. The latter is described with- 

 out a locality. 



DACTYLINA, Gray. 



D. Chiloensis, Molina. 



Pholas Chiloensis, Molina, Hist, de Chile, p. 179. 



id. Gmel., Syst. Nat. p. 3217. 



id. Gay, Hist, de Chile, p. 381, pi. 6, fig. 3. 



Dactylina Chiloensis, Chenu, Man. de Conch, v, 2, p. 4, fio-. 

 14, 15. 



