JJAZATLAN UNIVALVES 303 



arcuatis ornatis ; decumbente, vix spirali, pertinaciler affixu, 

 superficiem matricis parum erodente. 



Only one characteristic and one rubbed specimen were found 

 of this shell, which may be a Spiroglyphus. It has however 

 some characters in common with the young of the great Call- 

 fornian Vermetid, Aletes squamigerus. Long. '6, lat. apert. '13. 

 Hab. Mazatlan ; extremely rare, on Uvanilla and Cuma ; 



L'pool Col. 



Tablet 1484 contains the characteristic sp. 



353. ALETES MAEGARITARUM, Val. 



A. t. "A. centiguadro" simili, sed anfr. nucleosis iii. magis 

 elongatis ; anfr. normallbus r.apide augentibus ; adult a sub- 

 guadratd, ad angulas carivis nodosis conspicue ornatd ; liris 

 tenuioribus, vix decussatis. 

 Vermetus margaritaruin, Val. Voy. Yen. pi. 11, f. 2. 



Only one adult and two extremely young sp. were found, 

 which may not be conspecific. The nuclear whirls are not 

 globular, as appears the case in the only specimen seen of V. 

 centiquadrus ; in this respect it is intermediate between that 

 species and Bivonia. Long. 1*1 lat. apert. '3. 

 Hob. Mazatlan : extremely rare, on Spondylus ; L'pool Col. 



Tablet 1485 contains the youngest and the adult specimen. 



(TEN us VEBMETUS, Adanson. 



Testa plus minusve spiralis. Operculum magnum ; extus 

 laminis concentricisfoliaceis instructum : intus marginem versiis 

 convexum ; cicatrice musculari circulari, concentri.ee ccelatd. 

 Sen. p. 160, 1757. H. $ A. Ad. Gen. vol. i. p. 357. 



SECTION A. SPECIES TYPI 



Testdjuniore turritelloidea. Operculo colore corneo, tenuiore, 

 cxtus foliaceo ; cicatrice concentrice lirulatd. 



The turritelloid Vermetidae form a small but natural group ; 

 of which the species are distinguished by the sculpture of the 

 spiral portion, and of the operculum. 



