642 Haddon and Shackleton — A Revision of the British Actiniw. 



Locality.—^, and S. W. Ireland: — 50° 29' 26" N., 11° 4' W., 400 faths., July 

 11, 1889 (G-. C. Bourne): 500 faths., 54 miles off Achill Head, Co. Mayo, 

 July 10, 1890 (A. C. H.), (PI. lviii., fig. 25). The specimens figured on PI. lviii., 

 figs. 23. 24, are in the British Museum; they came from 71 miles W. by S. of 

 the Fastnet, 315 faths., and possibly also from deeper water {cf. Ann. Mag. Nat. 

 Hist. (6), IV., 1889, pp. 411, 430). 



The geographical distribution of this species is North Atlantic, extending from 

 the N. E. coast of America to N. W. Europe, in deep water. 



This is the largest and most striking of the species of British Zoanthese, and is 

 quite a recent addition to our fauna. 



The polyps are in two positions, one central and inferior, the remainder 

 marginal, divergent, and uniserial. The coenenchyme entirely surrounds the 

 shell on which it grows, save for the orifice through which the commensal hermit- 

 crab emerges. The orifice is ventrally situated, and is about 5 mm. distant from 

 the anterior border of the carcinseciuai, and is from about 15-20 mm. in diameter. 



Immediately behind the orifice is a polyp, which in spirit-specimens does not 

 rise above the general surface of the coenenchyme, and is less than 10 mm. in 

 diameter. 



The marginal polyps are prominent, and elliptical in section. At the 

 posterior end of the carcinaecium one polyp can readily be distinguished as being 

 markedly smaller (15mm. in height) than the other marginal polyps; this we 

 term the '' posterior polyp." There are in the three specimens which we have 

 examined four well -grown polyps to the left of the posterior polyp, and four, five, 

 and sis, respectively, on the right side of the carcinsecium. 



There is a space of 20 mm. between the right and left polyps on the anterior 

 convex border of the carcinaecium. Under-surface of the carcinsecium flat ; upper 

 surface irregularly convex, with the greatest prominence towards the right. 



A young specimen, which one of us dredged off the W. of Ireland, and which 

 is drawn of the natural size in PI. lviii., fig. 25, shows that the order of 

 the appearance of the polyps is probably as follows: — (1) the ventral polyp; 

 (2) the posterior polyp ; (3) the right and left anterior polyps ; (4) the succeeding 

 lateral polyps, of which the most posterior are the youngest. After four pairs of 

 marginal polyps have appeared the further production of polyps appears to be 

 confined to the right side. 



This species is always commensal with Eupagurus pilosimanus. 



Verrill first described this species in 1882 in the following terms : — " Polyps 

 few and very large, stout, with broad, swollen bases, arising from a very thick, 

 smooth, lubricous, gray or mud-coloured, translucent coenenchyme, which at first 

 invests small univalve shells, occupied by Parapagurus pilosimanus, but finally 

 grows far larger than the shell, and eventually absorbs it. Disc broad, larger 



