SERPULA. CREEPER. 149 



lar, a little curved at the smaller end and obliquely rounded 

 at the other, the pointed end colored with a mixture of 

 changeable purple blue or green : from the broad to the 

 pointed end run about eleven ribs, commencing on the car- 

 tilage side and extending over about two-thirds of the sur- 

 face, leaving the other part marked only by curved striae in. 

 an opposite direction ; inside smooth, perlaceous : length 

 three inches ; breadth six or more. 



Variety A. Smooth and without spines. 



Variety B. Furnished with concave spines, especially 

 along the ribs, which increase in size as they approach the 

 larger end. 



On the western coasts, v. v. 



3, Pinna inuricata. Prickly Nacre. 



Montagu, pi. 5. f. 3. 



Shell thin, brittle, semitransparent, flesh-color but darker 

 at the pointed end which is quite straight, obliquely rounded 

 at the broader end, with ten or twelve broad ribs running 

 from the larger to the pointed end covering the whole sur- 

 face of the shell, and marked with a few intermediate 

 smaller ones at the pointed end ; these ribs are furnished 

 with a few concave spines, chiefly towards the broader end ; 

 length about two inches ; breadth five or more. 



On the Dorsetshire coast : rare. v. m. 



SERPULA. CREEPER. 



Shell with a single valve, tubular, variously 

 shaped, sometimes divided by imperforated inter- 

 nal divisions at unequal distances. 



A. Attached, and spirally twisted, 1 to 9. 



B. Attached, and Irregularly twisted, 10 to 15. 



C. Detached, and curved or twisted, 16 to 20. 



D. Detached, and bottle-shaped, 21 to 29. 



A. Attached, and spirally twisted, 1 to 9. 

 1 . Serpula spirorbis. Spiral Creeper. 

 Lister, pi. 553. f. 5 Pennant, pi. 94. f. 1 Da Costa 9 

 o 3 pi. 2. 



