MAZATLAN UNIVALVES 411 



489. ODOSTOMIA LAMELLATA, n. s. 



O. t. conicd, turritd, solidd, albd ; vertice nucleoso satis 

 magno, declivi, maximam partem truncations tegente ; anfr. 

 normalibus subplanatis, Icevibus, ctd peripJieriam angulatis, 

 hand carinatis ; sutura parum impressd ; plied magnd, extante, 

 lamellosd, declivi. 



The description is compiled from portions, the only perfect 

 specimen found having been broken under the microscope. 

 This species, if it 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. '! + , lat. "04, div. 23. 

 Hal. Mazatlan ; 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 STIBSULCATA, n. s. 



O. t. " O. lamellatce" simili ; sed anfr. planatis, peripkerid 

 vix carinatd, plied obtusd, solidd, transversd ; vertice nucleoso 

 ut in " 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. 



Hob. Mazatlan; 4 imperfect sp. off Chama; L'pool Col. 

 Tablet 1955 contains 2 specimens. 



SECTION B. Peritreme continuous. 



491. ODOSTOMIA VALLATA, n. s. 



O. t. conicd, parvd, subdiapJiand, tenui, albd ; vertice nucleoso 

 parvo, parum declivi, dimidium truncations tegente; anfr. 

 normalibus iii. et dimidio, planatis, sutura effbssd ; carinuld, 

 super fossam, et spir am et peripJieriam decurrente ; peripkerid 

 acute angulatd, basi planatd, umbilico conspicuo ; aperturd 

 continud ; plied obtusd, transversd, celatd, juxta parietem sitd. 



This beautiful little species, of a semi-transparent chalce- 

 donic texture, is remarkable for its exactly conical form, well 



