MOLLUSCA. sEitPULA. 9 



glossy surface, and above all, by the absence of any flattening of 

 the outer whorl where it rests upon its residence. The whorls 

 are so loosely connected as sometimes to be entirely distinct ; and 

 the aperture frequently looks directly upward. Aperture cir- 

 cular. 



This species is more common than the preceding, and is found 

 grouped in a similar manner upon fuci, stones, &c. It is the 

 Serpula spirillum of Linnaeus. 



SPIRORBIS SINISTRORSA. 

 State Coll., No. 263. Soc. Cab., No. 2314. 



A third species, which I take to be the one above named, I 

 have seen only upon stones and shells drawn up by fishing lines at 

 St. George's Bank. It is a smooth, glistening, translucent shell, 

 with three or four whorls, turning in opposition to the sun. The 

 whorls are nearly distinct from each other, not always preserving 

 a regular spiral, but occasionally stretching out for some distance 

 in a straight direction ; one whorl generally lies upon another, so 

 that the outer whorl seldom touches the object on which the shell 

 rests. Diameter about } inch. It was first described by Mon- 

 tagu, under the name of Serpula sinistrorsa. (FIGURE 4.) 



/ 

 GENUS SERPULA, Lm. 



Tubes solid, calcareous, irregularly coiled, solitary or in groups, 

 permanently adherent aperture terminal, rounded, simple. 



It is probable that several species of this genus live on our 

 coast. They attach themselves to stones, pieces of wood, and 

 shells of the mollusca and Crustacea ; and such of them as we 

 meet with are generally thrown up from the deep by violent 

 storms, or conveyed from warm climates on the bottoms of vessels. 

 They grow to a much larger size than Spirorbis, and are chiefly 

 distinguished by not observing any regularity in the arrangement 

 of their convolutions. I am not certain that we have more than 

 one species habitually living on our coast. 

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