Gutty Marine Laboratory, St. Andrews. 33 



angle, wliilst the prow is contiuued beyond it to end in a 

 process tor a ligament, and the base is convex inferior ly 

 and has a process at the end of the posterior outline. 



The cephalic region of the generally distributed Poly- 

 cirrns auraiitiacns, Grube, the nineteenth form, has even more 

 voluminons folils than in Ereutho, the plate being frilled 

 anteriorly as well as forming the two broad folds posteriorly. 

 Moreover, dorsally is an indication of a collar in the shap3 

 of a smoothly rounded ridge, the wiiole being occasionally 

 spread as a wide border to the oral region, which thus 

 assumes the form of a shallow funnel. The entire outer 

 surface gives origin to the dense series of dull yellow ten- 

 taclas, which form a seething mass of threads — slender, 

 flattened, and fusiform. Each tentacle extends even to a 

 greater degree than in the red variety, becoming paler when 

 stretclied, though still retaining a trace of the yellow hue. 

 Their extensibilii;y and elasticity are remarkable, and the 

 thinnest strand presents a minutely cellular appearance with 

 a central streak. The smaller and siiorter tentacles occu[)y 

 as usual the edges of the posterior lobes, so that when the 

 flaps are adpressed they are close to the fissure leading to 

 tJie mouth. In the red variety the tentacles form au inex- 

 tricable mass in a vessel — enclosing other annelids, fragments 

 of shells, Balani, and mud. When much stretched the tip, 

 which is generally the widest part, is pinkish, the attenuate 

 region below it being pale, and the intermingling of these 

 hues, especially against a dark background, is striking. 



A specimen of moderate size can stretch its tentacles 

 three or four inches, the processes being dilated at the tip, 

 but of extreme tenuity toward the base, and the corpuscles 

 of the coelomic fluid are observed in the centre. 



When viewed from the dor^nm the slight dorsal collar 

 runs on each side and bends downward behind the pro- 

 jecting fold of the anterior arch, and it sometimes ha[)i)ens 

 that a median fold in front divides the tentacles into two 

 symmetrical series after the manner of Phoronis. 



Instead of the single large post-oral scute of Ereutho., 

 Polycirrus has a tongue-shaped median glandular process, 

 the edges of which are free, and the anterior border runs 

 smoothly forward to the mouth. In one example this 

 process is bifid posteriorly, whilst a small area is cut off 

 anteriorly, the whole being symmetrical. It may represent 

 the first scute. 



The body resembles that of Ereutho, and, like it, is in 



Ann. dc Mag. X. IJist. Ser. 8. Vol. xv. 3 



