Spio? vulgaris. 335 



taculum longer than the rest, and to which the term antenna 

 might with greater propriety be applied than to the others. Still 

 exterior to these there are, on each side, a pair of ac-cular-pointed 

 filaments. It appears then that there are nine tentacula divisible 

 into three classes, and readily distinguishable by their figure, 

 viz. two short and cranial ; two long, conical, originating under 

 the head ; and five acicular-pointed, which probably spring from 

 the body, but which differ from their lateral analogues in being 

 non-retractile. It might be proper to designate these by dis- 

 tinctive names ; but however we call them or divide them, we 

 shall not be able to make them coincide with the characters of 

 Lamarck. 



Fam. Ner^idiSes. Lamarck. 

 Gen. Spio ? Id. 



/ Spio vulgaris. 

 Desc. Bodi/ three inches in length, vermiform, depressed, 

 quadrangular, narrowed a little at the head, tapered gradually 

 towards the anal extremity, of a yellowish brown colour, stained 

 longitudinally on both surfaces with the large intestine, and 

 marked transversely with numerous close -set dark -red striae. 

 Mouth terminal, inferior, with black margins. From it projects a 

 triangular process^ the base of the triangle being outwards, and 

 each angle produced into a conical process. This process is 

 retractile. Head small, slightly emarginate in front, marked 

 above with three black spots or lines, and four very small ei/es 

 placed thus (*..•) Antennce two, setaceous, white, obscurely 

 spotted, half an inch long, approximate at the base, placed on the 

 vertex, contortile, and capable of being rolled up in a spiral form. 

 Segments very numerous. Each segment has on each side, affixed 

 to its dorsal margin, a subulate branchial process ^ nearly as long 

 as the breadth of the animal, of a fine red colour, and sometimes 

 spotted. These, when in water, are raised and extended, and in 

 perpetual motion, but when at rest or removed from the water, 

 they are laid obliquely across the back, their points meeting in 

 the middle, and hence give the animal the appearance of being 

 marked with transverse striae. Beneath these are placed ihcfeety 

 viz. a papilla divided into two processes, one of which is simple, 



