SERPULA. 1075 



lata, from which it may readily be distinguished by the bi- 

 dentated aperture. 



HETEROSTROPHA. 14. Shell taper, spiral, with three 

 elevated ribs on the upper side, and the whirls 

 reversed. 



Serpula heterostropha. Montagu Test. p. 503. Maton 

 atid Racket, in Lin. Trans, viii. p. 242. 

 Inhabits the sea on oysters and other shells, and marine Algae, 



in Kingsbridge Bay, Devonshire. Montagu. 

 Shell thick, brownish or dirty white, and not half the size of 



S. granulata, from which it also differs in having the whirls 



reversed. 



coRRUGATA. 15. Shell regular, spiral, transversely 

 wrinkled, and umbilicated. 



Serpula corrugata. Montagu Test. p. 502. Maton and 

 Rackety in Lin. Trans, viii. p. 242. 



Inhabits the sea on slate rocks, at Milton, Devonshire. Mon- 

 tagu. 



Mr. Montagu says that this is a much stronger shell than S. 

 Spirillum, and never exposes so much of the second volu- 

 tion to view, and that, though more wrinkled, it possesses a 

 superior gloss when cleared from extraneous matter. 



XuciDA. 16. Shell taper, spiral, very smooth and 

 glossy ; whirls reversed. 



Serpula lucida. Montagu Test. p. 507. Maton and Rac- 

 ket, in Lin. Trans, viii. p. 243. 

 Serpula reflexa. Adams in Lin. Trans, v. p. 4. t. 1. f. 31 

 and 32. 

 Inhabits the sea, on Sertularia abietina very frequent, and some- 

 times on Sertularia argentea. Montagu. 

 Shell half a line in diameter, and distinguishable from its con- 

 geners by its extremely smooth, glossy, and vitreous appear- 

 ance ; whirls two or three, irregular, sometimes lateral, and 

 sometimes turned over each other, with the aperture project- 

 ing upwards, and not unfrequently unconnected. S. cornea 

 of Adams appears to be a very doubtful species, and not 

 worth notice. 



VITREA. 17. Shell taper, regularly spiral, orbicu- 

 lar, and wrinkled ; aperture thickened. 



