MAZATLAN UNIVALVES 411 



489. Odostomia lamellata, n. s. 



0. t. conicd, turrita, solidd, alba ; vertice nucleoso satis 

 magna, declivi, maximam partem tnincationis iegente ; anfr. 

 normalihus subplanafh; Icevibus, ad pe?'ipheriam angulatis, 

 hand carinatis ; suturd paruin impressd ; plied magna, extante, 

 lamellosd, declivi. 



Tlie 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 angidated. It probably had 

 five normal whirls, and measured long. '! + , lat. '04, div. 23". 

 JBTaS.— 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 sttbsttlcata, n. s. 



O. t. " 0. lamellatce" simili ; sed anfr. planatis, peripherid 

 vix carinaid, plica obtusd, solidd, transversa ; vertice nucleoso 

 ut in " 0. 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 lo7ig. '044, lo7ig. spir. '024, 

 lat. -028, div. 30". 

 JHa6.— Mazatlan ; 4 imperfect sp. off Chama ; L'pool Col. 



Tablet 1955 contains 2 specimens. 



Section B. Periireme continuous. 



491. Odostomia vallata, n. s. 



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

 parvo, paruni declivi, dimidium truncationis tegente ; anfr. 

 normalibus iii. et dimidio, pla)iatis, suturd, effbssd ; carinuld, 

 super fossam, et spiram et peripheriam dectirrente ; peripherid 

 acute angulatd, basi planatd, umbilico conspicuo ; aperturd 

 coniinud ; plied ohtusd, transversa, celatd, juxta parietem sitd. 



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

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



