262 HETEROCIRRUS VIRIDIS. 



peristomium, bearing two large muscular and grooved tentacles, and a pair of branchiae 

 beneath them. 



Body about half an inch long, and having from fifty to eighty-six segments. The 

 third segment bears bristles, and the third bristled segment has ventrally bifid hooks, 

 which continue to the posterior end. The dorsal bristles likewise occur throughout except 

 near the anal segment, where two hooks occur with them and dorsal bristles. Colour 

 greenish or yellowish. 



Hooks with a large and not very acute main fang, a spike above it, a slightly curved 

 shaft with an enlargement at the shoulder. 



Synonyms. 

 1880. Girratulus viridis, Langerhans. Zeitschr. f. wiss. Zool., Bd. xxxiv, p. 98, Taf. iv, fig. 9. 

 1894. Heterocirrus flavoviridis, De St. Joseph. Ann. Sc. nat., 7 e ser., t. xviii, p. 54/ pi. iii ; fio-. 61. 

 1898. „ „ Caullery and Mesnil. Annales Univ. Lyon, fasc. xxxix, p. 117. 



1910- > } viridis, Elwes. Journ. M. B. A., vol. ix, p. 63. 



Habitat. — Occasionally in small pools in limestone rocks at Babbacombe (Elwes). 



The head forms a more or less pointed cone with two conspicuous eyes posteriorly. 



The body in the preparation is thickest anteriorly, tapering only a little to the conical 

 snout. It is about half an inch in length, and has from fifty to eighty-six segments. It 

 tapers gradually from the anterior region to the tip of the slender tail which has the anus 

 at the tip. It is characterised by the numerous filaments which stretch on each side from 

 the tentacles backward, and which give it a woolly appearance. The colour is greenish 

 or yellow, though in the preparation it is blackish. The tentacles are long, grooved, 

 ciliated, and can be moved actively or coiled in a spiral ; whilst beneath each is a branchial 

 filament. The next two segments (third and fourth) bear bristles both dorsally and 

 ventrally and they curve backward. In the following segment bifid crotchets appear in 

 the ventral division, and are continued to the posterior end. At the thirteenth segment 

 four of the five capillary bristles disappear, and two hooks of the same structure as the 

 ventral accompany the single bristle to the posterior end (De St. Joseph). The bristles are 

 longest anteriorly, and soon become short and thus are in marked contrast to those of 

 certain forms, the long caudal bristles of which are so conspicuous, yet they are also 

 directed forward. De St. Joseph thought that it agreed with Heterocirrus caput-esocis in 

 its segmental organs and anal segment. Further that it approached the Heterocirrus 

 (Girratulus) fragilis of Leidy, and the Girratulus viridis of Langerhans, both of which had 

 eyes and bifid hooks, but the tentacles in the former arise on the second setigerous segment 

 and in the latter on the first setigerous segment. There is little doubt that the species of 

 Langerhans is identical with that of De St. Joseph. 



This is one of the species which the patient and acute Baron de St. Joseph added to 

 the French fauna from the shores of Dinard, which he has made classic by his able 

 researches on the annelids. It appears to be a southern type, and a single example was 

 procured by Major Elwes, who kindly presented the mounted preparation. 



In Heterocirrus viridis MM. Caullery and Mesnil discovered a Haplosjporidium (H. 

 heterocirri) — probably in the perivisceral cavity. Mesnil again (1901) witnessed regene- 

 ration of the anterior region in the same species. 



