354 TEREBRATULIDiE. 



Animals, p. 369.— Brit. Marine Conch, p. 127. — Brown, 

 Illust. Conch. G. B. p. 68. 

 Terehratulina caput-serpentis, D'Orbigny, Pal. Franc. T. C. vol. iv. p. 58. 

 Davila, Catalog. Cabinet, yoI. i. pi. 20, f. F. — Foli, Test. Sicil. vol. ii. pi. 30, 

 f. 15 (part of gronp). — Encycl. Method. Vers, pi. 246, f. 7. 



Although Hable to no inconsiderable amount of vari- 

 ation in form, this shell is always more or less of a rounded 

 pentagonal, and somewhat egg-shaped figure, its general 

 outline ranging from narrow subovate to broadly obovate ; 

 the distance from the beaks to the base always exceeds 

 (and very greatly so in the young) the space between the 

 lateral extremities. Its valves, which are moderately and 

 not very unequally ventricose, are slightly translucent, 

 devoid of polish, not very thin, and of an uniform squalid 

 white, but frequently appear stained with two bufl:-coloured 

 spots, which, however, are only the result of the imperfect 

 removal of the animal. The surface is everywhere covered 

 with very numerous radiating dichotomous or forked 

 costellse, which are generally of the same breadth as their 

 interstices, and are far coarser in the fry (and consequently 

 upon the umbonal region of the adult) than towards the 

 slightly emarginated base of the mature shell ; which 

 difference, the absence of basal retusion at that stage of 

 growth, and the circumstance (not unusual at any period 

 of increase) of being found invested with a supposititious 

 epidermis of downy sponge, induced the early separation of 

 the young under the epithet pubescens. The marginal line, 

 which is delicately svibcrenulated within, is flexuous at the 

 sides, and the lateral edges of the smaller valve approach 

 each other at the beak in an angle, that is usually an 

 acute one in the young, a right or even a slightly obtuse 

 one in the adult. The larger valve is somewhat rostrated ; 

 the perforation is moderate in size, somewhat oblique, 

 and not entire. The cardinal area is rather flattened, and 



