248 MAZATLAN UNIVALVES 



Hal. Mazatlan ; extremely rare, on Chama and Spondylus ; 



L'pool Col. 



Tablet 1163 contains the perfect specimen. 



GENUS PLIOTIA, Gray, 



Syn. B. M. 1840. JET. Sf A. Ad. Gen. vol. i. p. 404. Phil. 



Handb. Conch, p. 206. 

 Delphinula, pars, auct. 



The following shells are ranked doubtfully with this genus, 

 not having the expanded lip of the typical species, and the 

 opercula being unknown. 



313. P LlOTIA CAEINATA, n. S. 



?L. t. solidd, cinered, rufo tinctd ; spird depressd, anfractibus 

 iv. supra subplanatis, suturd distinctd, angulatd ; carinis iv. 

 extantibus circa peripJieriam ; liris spiralibus iii. in spird, 

 nodulosis ; iii. in basi rotundatd, Jiaud extantibus ; circa um- 

 bilicum magnum radiatim rugoso-nodosd ; aperturd intus circu- 

 lari, anfr. penult, parum attingente ; anfractu ultimo valde 

 decumbente. 



Shell comparatively solid and opaque ; it may be young, but 

 from the small size of the nuclear portion and the sudden 

 declension of the last whirl, it is presumed to be nearly mature. 

 Long. '03, lat. '045 by '04, div. (anfr. penult.) 175. 

 Hob. Mazatlan ; 1 sp- on Spondylus ; L'pool Col. 



Tablet 1164 contains the specimen, 



314. PLlOTIA STEIULATA, n. S. 



?L. t. turbiniformi, spird subelevatd, albidd, solidd ; anfracti- 

 bus iii. rotundalis, radiatim exillime et confertissime striulatis, 

 carinis parum extantibus iii. spiralibus ; umbttico magno ; in 

 basi interdum rugis radiantibus ; aperturd declivi, solidissimd, 

 intus rotundatd, anfr. penult, parum attingente. 



The thickness of this little shell is extraordinary, being at 

 the posterior portion of the aperture nearly '005 in. The 

 whirls are rounded, obscurely carinated, and most minutely 

 and closely striated in the direction of growth. Long. '027, 

 lat. '037 by '03, div. 130. 



