MAZATLAN UNIVALVES "41h 
489, ODOSTOMIA LAMELLATA, 7%. S. 
O. t. conicd, turritd, solidd, alba; vertice nucleoso satis 
magno, declivi, maximam partem trunecationis tegente; anfr. 
normalibus subplanatis, levibus, ad peripheriam angulatis, 
haud carinatis ; suturd parum impressa ; plica magna, extante, 
lamnellosd, declivi. 
The description is compiled from portions, the only perfect 
specimen found having been broken under the microscope. 
This species, ifit had secondary plaits, would rank with Obelis- 
cus. It closely resembles O. canaliculata, C. B. Ad. Contr. 
Conch. no. 7, p. 109) from Jamaica; but differs in being a 
wider shell, with the base more angulated. It probably had 
five normal whirls, and measured long. ‘1+, lat. 04, div. 23°. 
Hab.—Mazatian ; portions of 4 sp. off Chama; L’pool .Col. 
Tablet 1954 contains the young and old portions from which 
the complete idea may be constructed. 
490. ODOSTOMIA SUBSULCATA, 2. S. 
O. t. “O. lamellate” simili; sed anfr. planatis, peripheria 
vix carinatd, plicd obtusd, solidd, transversa ; vertice nucleose 
A 99 
utin *O. vallatd. 
Differs from O. mammillata and O. vallata in the solid texture 
of the shell, and strength of the plait. A young shell, with 
three normal whirls, measures long. ‘044, long. spir. ‘024, 
lat. °028, div. 30°. 
Hab.—Mazatlan ; 4 imperfect sp. off Chama; D’pool Col. 
Tablet 1955 contains 2 specimens. 
j 
Srotion B. Peritreme continuous. 
491. ODOSTOMIA VALLATA, 7. S. 
O. t. conicd, parva, subdiaphanda, tenw, albé ; vertice nucleoso 
parvo, parum declivi, dimidium truncations tegente; anfr. 
normalibus ii. et dimidio, planatis, suturd effossa ; carinuld, 
super fossa, et spiram et peripheriam decurrente ; peripheria 
acute angulata, basi planata, umbilico conspicuo; apertura 
continua ; plica obtusa, transversd, celatd, juxta parietem sité, 
This beautiful little species, of a semi-transparent chalce- 
donie texture, is remarkable for its exactly conical form, well 
