308 



SOLARIELLA. 



This genus was founded by Wood for an English (Yair fossil 

 Trochid, conical in form, with tubular whorls and deep umbilicus, 

 its margin crenulated. The type species, S. maeidata, is closely 

 allied to the recent S. amabilis of Jeffreys. The name has been 

 erroneously used by the brothers Adams for a group of tropical, 

 broadly umbilicated, tubular-whorled Trochids, which later received 

 the name Minolia. In 1877, Herman Friele instituted the genus 

 Machceroplax (type M. affinis Jeffr., amofoYw JefFr. var.), giving as 

 diagnostic characters the short broad radula, with few (about 10) 

 uncini, and these much larger and differently formed than in 

 Margarita. The characters of radula may be compared thus : 



Margarita. 



Radula long. 



Median teeth 9-13, subequal, 

 with recurved serrate cusps, 

 and an outer obsolescent cusp- 

 less plate lying between the 

 perfect median teeth and the 

 uncini. 



Uncini very numerous, the apices 

 recurved, denticulate. 



| Mack&oplax ( Solar iella). 



Radula short, broad. 



Median teeth 5-7, subequal, with 

 serrate cusps, the obsolescent 

 outer lateral of Margarita re- 

 placed by a well -developed 

 tooth with denticulate cusp. 



Uncini few (about 10), large r 

 falciform, with entire or feebly 

 denticulate ed<res. 



The little group separated by the writer under the name Conotro- 

 chus may, as Dr. Dall has suggested to me, belong to Solariella ; but 

 as its relations seem to be equally close to Minolta, 1 include it for the 

 present in that genus as a section. (See page 197, 268.) 



The dentition and operculum of 8. varicosa arc figured on pi. 50, 

 figs. 7, 17. 



S. OBSCURA Couthony. PI. 57, figs. 44, 45. 



Shell umbilicate, conical, thin, ashen, whitish or reddish in color ; 

 surface lusterless, the dull outer layer very thin, overlying a brill- 

 iantly iridescent nacre. Sculpture consisting of a rather prominent 

 spiral ridge or carina at the shoulder of each whorl, beneath which, 

 on the peripheral portion of the whorl, there are several (generally 

 3 to 6) smaller Iira3, often subobsolete ; the entire base sometimes 

 shows fine low concentric liraB, but usually they nearly disappear 

 there, becoming visible again around the umbilicus ; there are often 

 traces of a few obscure spiral riblets above the supra-peripheral 

 carina. Longitudinally the entire surface is marked by regular, 



