MAZATLAN UNIVALVES 431 



B. Whirls with spiral sculpture, 

 (a.) Ribs interrupted at the periphery. 



529. CHEMNITZIA , sp. ind. (d.) 



Tablet 2000 contains a fragment of a very large, white, sub- 

 diaphanous species, with deep grooves between ribs ending at 

 the periphery. The mouth must have been '08 long. 

 Hah. Mazatlan ; fragment, off Spondylus ; L'pool Col. 



530. CHEMNITZIA GEACILLIMA, n. s. 



Ch. t. juniore acutisGimd, maxime elongatd ; vertice nucleoso 

 prolongato, marginibus spires incurvatis 1 super ante ; anfr. 

 primis solutis, rotundatis ; postea subplanatis ; costis circ. xvi. 

 obtusis, circa penpheriam subito truncatis ; basi rotundatd, 

 IcBvi ; interstitiis spiraliter tenue decussatis ; aperturd elongatd ; 

 columelld vix intortd. 



In most Chemnitzise, even if the spire outlines are nearly 

 parallel in the adult, they are divergent when young. In this, 

 the upper whirls are the sharpest, and scarcely overlap each 

 other. The nucleus appears to have been very large. A worn, 

 dead sp. appears even sharper than that here measured, with 

 fewer ribs. The larger sp. with eight normal whirls, measures 

 long. '117, long. spir. '085, lat. "008 "035, div. 13. 

 Hob. Mazatlan ; 2 sp. off Chama ; L'pool Col. 



Tablet 2.001 contains the larger specimen. 



(b.J Ribs evanescent at the base. 



531. CHEMNITZIA UNDATA, n. s. 



Ch. t. gracili, tenui, albido-fuscd ; vertice nucleoso marginibus 

 spircB subrectis super ante ; anfr. (teste juniore) vii. subplanatis, 

 suturd profundd ; liris tenuissimis circiter xviii. acutis, vix 

 expressis, circa basin evanidis, interstitiis latis, undatis ; striulis 

 spiralibus totam superficiem ornantibus, stria majore circa 

 peripheriam ; labro acuto ; columelld gracili, vix tortd. 



On comparing this shell with the corresponding portion of 

 C. gracilior, C. B. Ad., it is found to have many fewer and 

 much finer and sharper ribs, which do not end at the periphery, 

 like the curved interspaces. Long. '065, long. spir. "045, 

 lat. '022, div. 14. 



Hob. Mazatlan ; 2 young perfect sp. off Spondylus; L'pool Col. 



