MICROCERAMUS. 163 



Group of M. elegans. 



Imperforate or shortly rimate, thin, marked with opaque 

 white on a brownish-corneous, somewhat translucent ground. 

 Suture not distinctly or regularly denticulate; basal keel 

 very weak or wanting. Sculpture of rib- or thread-like striae, 

 which often terminate in a series of little beads above the 

 suture. Columellar margin not built forward from the colu- 

 mella proper, or but slightly so. Central Cuba, extending 

 from Cabo Cruz to Pinar del Rio. 



I. Spire almost straightly conic. 



1. Maculate and interruptedly banded with white. 



a. Very closely, finely striate; suture simple; last 

 whorl rounded. Western Matanzas. 



M. palenquensis, no. 11. 



&. Sculptured with thread-like rib-striae, often 

 beaded above the suture; last whorl suban- 

 gular. Pinar del Rio. 



M. elegans, no. 10, and M. e. infradenticu- 

 latus, no. 10a. 



2. Rib-striae white on a darker ground. 



a. Shell conic, whorls 8-9. Havana prov. 



M. p. perconicus, no. 12a. 



b. Shell long, turrite, whorls 9-10. Santa Clara. 



M. angulosus, no. 13. 

 II. Spire attenuate above, then swollen. 



1. Rimate, corneous marbled with white ; a low, hardly 

 noticeable basal keel; closely sculptured with nar- 

 row riblets. M. petitianus, no. 12. 



2. Perforate, closely rib-striate, nearly uniform gray; 

 7.3 x 3.5 mm., with 8 whorls. Eastern Cuba. 



M. simplex, no. 15. 



3. Imperforate, very closely, finely striate ; 8 x 4.6 mm., 

 with 8 whorls. M. palenquensis, no. 11. 



4. Imperforate, with close, whitish riblets; 5.6x2 mm., 

 with 9 whorls. E. Cuba. M. minor, no. 14. 



