Dr. Johnston on the British Aphroditacece. 427 



difications of the same organs, in those Annelides which are 

 not shielded with dorsal scales, — an opinion which from the 

 dissimilarity of their position on the body we might otherwise 

 have hesitated to adopt. The feet of the Aphroditacece are 

 divided into two branches, each furnished with a spine, with 

 bristles, and with cirri, whose figures vary according to the 

 species. We have spoken above of the superior cirri: the in- 

 ferior are found on all the feet and offer nothing remarkable 

 for notice, unless on the first segment, where they are very 

 large, and with the superior, constitute tentacular cirri, a sort of 

 antennaeform filaments placed at each side of the head. But the 

 true antennae, however similar in appearance, are readily distin- 

 guished from them by their insertion on the head itself: of these 

 we generally reckon three*, a middle one and one on each side; 

 and under and exterior to them there are two larger setaceous 

 filaments, which may without impropriety be denominated 

 palpi, since they are used to feel the way during the creature^s 

 progress. The eyes are black points on the upper surface of 

 the head, usually four in number, sometimes only two, and in 

 ligation their existence is doubtful. From the mouth a pro- 

 boscis is at pleasure evolved, which is armed with four jaws 

 united in pairs, two above and two below, opposed the one to 

 the other by their cutting edge ; and this disposition is one of 

 the peculiarities of the family, for in the Euniceacece there are 

 never less than seven jaws, and in the Amphinomenacea there 

 are none. Such also is the case with many of the Nereides, 

 although several genera in this family have two jaws, and a 

 few even four ; but the pairs, unlike those of Aphroditacece, 

 are perfectly distinct and widely separate. 



The British species of this family are few in number, so far 

 as has been ascertained, and are referable to the four following 

 genera. 



1. Aphrodita. Body squamous, the scales and superior 

 cirri not coexistent on the same foot, but alternating; 



* Savigny and Audouin and Milne Edwards say five ; but if we limit, as 

 I think we ought, the term antenna to those filaments which are strictly 

 cranial, there are only three ; and what these celebrated naturalists call ex- 

 ternal antenna, I have, in the following descriptions, called palpi, since they 

 originate under the head, and are obviously different in structure, as they 

 appear to be, also, in their functions. 



