244; MAZATLAN UNIVALVES 
umbilicum et inter carinas centrales evanidis ; aperturd &@ 
carims angulatd, inter duas carinas anfr. penult. attingente ; 
anfr. ult. plus minusve decunbente. 
Pan. Shells, no. 259, pp. 184, 315. 
Having written the above description (under the name of 
V. trigonata), a minute examination of the type specimens in 
Mr. Cuming’s collection proves them to be identical with the 
Panama shell. It is remarkable that Prof. Adams has not 
mentioned the stout keel above the periphery, nor the crowded 
spiral strize over the surface, which however are clearly marked 
on his specimens. Jf there are similar omissions in other 
diagnoses; it may be that some of the other species have been 
before described. The typical markings are with transverse 
riblets, about 20 to the whirl, on the outer half of the base, and 
between the keels on the spire: but in one specimen are nearly 
double that number. The spiral strie are over the whole 
surface. The keels are sharp, smooth, and extremely promin- 
ent. It is difficult to estimate the divergence, as it depends 
on the depression of the last whirl, which in one of the adult 
specimens makes the angle 150°, in the other 170°. Long. °025, 
lat. °06 by °05. 
Hab.—Panama; 7 sp.in sand; C. B. Adams.—Mazatlan ; 2 
adult and 4 young sp. off Spondylus and Chama; L’pool Col. 
Tablet 1156 contains the most characteristic specimen. 
306. VITRINELLA CORONATA, %. S. 
Vit. “V. exique” simili, sed discoided, striis spiralibus nisi 
in umbilicum nullis, seu evanescentibus ; basi prope wmnbilico 
valde an gulato ; carind medida maxime extante ; rugis radianti- 
bus, in Jumore valde extantibus, intus carinam basalem, et supra 
spiram, carinam posteriorem in spird superantibus, quasi coron- 
antibus. 
The distinguishing radiating ruge which cross the keel on 
the spire and give it a serrated or coronated appearance are 
very conspicuous on the young shell; but, along with those 
on the base, they become evanescent as the shell arrives at 
maturity. The species is further distinguished from V. ex- 
igua by the absence of spiral strie except in the umbilicus ; 
and from both this and V. tricarinata by its extremely depress- 
ed growth, the upper keel completely hiding the spire. Only 
one perfect and 3 imperfect specimens were found. Long. °02, 
lat. "055 by °045, div. 185°. 
