MAZATLAN UNIVALVES 303 
arcuatis ornatis ; decumbente, via spirali, pertinaciter affixé, 
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 Cali- 
fornian Vermetid, Aletes squamigerus. Long. ‘6, lat. apert.*13. 
Hab.—Mazatlan ; extremely rare, on Uvanilla and Cuma; 
LI’pool Col. 
Tablet 1484, contains the characteristic sp. 
353. ALETES MARGARITARUM, Val. 
A. t. “A. centiquadro” simili, sed anfr. nucleosis 11. magis 
elongatis ; anfr. normalibus rapidé augentibus; adulid sub- 
quadrata, ad angulas carinis nodosis conspicue ornata ; liris 
tenuioribus, via decussatis. 
Vermetus margaritarum, Val. Voy. Ven. pl. 11, f. 2. 
Only one adult and two extremely young sp. were found, 
which may not be conspe@ific. The nuclear whirls are not 
globular, as appears the case in the only specimen seen of V. 
eentiquadrus ; in this respect it is intermediate between that 
species and Bivonia. Long. 1°1 lat. apert. °3. 
Hab.—Mazatlan: extremely rare, on Spondylus ; L’pool Col. 
Tablet 1485 contains the youngest and the adult specimen. 
Genus VERMETUS, Adanson. 
Testa plus minusve spiralis. Operculum magnum ; extus 
laminis concentricis foliaceis instructum : intus marginem versus 
convexum ; cicatrice musculart circulari, concentrice celata. 
Sen. p. 160, 1757.—H. & A. Ad. Gen. vol. 1. p. 357. 
Section A. SPRcrIES TYPICI. 
Testa juniore turritelloided. Operculo colore corneo, tenuiore, 
extus foliaceo ; cicatrice concentricé lirulatd. 
The turritelloid Vermetide form a small but natural group ; 
of which the species are distinguished by the sculpture of the 
spiral portion, and of the operculum. 
