658 MR J. T. CUNNINGHAM AND MR G. A. RAMAGE ON THE 



the 21st somite, counting the buccal as the 1st. It consists of 5 or 6 somites; 

 it is bent down towards the ventral side; its first somite bears two series of 

 spines, representing the notopodia; the dorsal surface of the scapha is concave, 

 and its lateral margins are thin and crenulated; it terminates in a spatulate 

 membrane overhanging the anus. The scapha fills up the lumen of the tube, 

 which the animal inhabits, posteriorly, as the palmulse, and the flat surface 

 behind them occlude the tube anteriorly. 



Anatomy. — (See PL XLII. fig. 20 e). — In Pectinaria the arrangement of the 

 dorsal blood-vessel is similar to that seen in Amphitrite ; the intestine close 

 behind the mouth is bent into a long S-shaped loop ; the pharynx is narrow, 

 then opens into a thick-walled smooth portion, extending nearly to the 

 posterior end of the thorax, this turns forward as a thin-walled yellow portion, 

 which reaches forward to the pharynx, and then turns back again, as a very 

 thin-walled transparent portion full of sand. The dorsal blood-vessel on the 

 first of these portions is ventral, and is formed by blood-sinuses on the gut 

 communicating with a ventral sinus ; the latter at the commencement of the 

 narrow pharynx forms a circumintestinal ring, which opens into the dorsal 

 " heart," as in Amphitrite. The heart contains a cellular " cardiac body." 



There are three pairs of nephridia in Pectinaria, of which the first pair are 

 the largest ; all the organs are of the usual type, each consisting of a tube bent 

 upon itself, and provided with a nephrostome, and an opening to the exterior. 

 There is a transverse septum separating the buccal somite from the following. 

 The nephrostome of the 1st nephridium is on the anterior side of this septum ; 

 the nephridia are brown or black in colour, and this most exterior one reaches 

 dorsalwards above the intestine. The anterior nephridium opens to the exterior, 

 some little space ventral of the origin of the 1st bronchia. Between the 

 nephridial opening and the root of the branchia is the opening of a peculiar 

 glandular organ, whose function we have been unable to ascertain. On 

 dissection of a fresh specimen, this gland is seen as a milk-white opaque 

 cylindrical body, about J-th inch long (PL XLII. fig. 20 e, w), free everywhere, 

 except at the point where it is continuous at its external aperture with the 

 body-wall. The efferent duct of this gland is lined by a high columnar 

 epithelium, of which the component cells are solid and columnar ; throughout 

 the rest of the gland, though there is a layer of long solid nucleated cells near 

 the basement membrane, these are covered by other layers of large vacuolated 

 cells, whose walls form a network almost, but not quite obliterating the lumen 

 of the gland. The wall of the gland is well supplied with pseudhsemal vessels. 

 The 2nd branchiferous (i.e., 3rd) somite and the following are unprovided with 

 nephridia ; but the latter, i.e., the 4th somite, contains a nephrostome belonging 

 to the nephridium of the 5th somite ; the 6th somite is also provided with a 

 nephridium, whose nephrostome is in the 5th somite. The nephrostomata are 



