638 Haddon and Shackleton — A Revision of the British Actinice. 



this species. Verrill, however, erected a new species for the forms dredged off the 

 east coast of N. America. Thanks again to Canon Norman's courtesy we have 

 examined some of Professor Verrill's specimens, and we must confess to not being 

 able to distinguish them specifically from the European examples. It is difficult 

 to understand why Professor Hertwig ignored these two specific names and 

 adopted for his specimen (Challenger Sta., 49, off Nova Scotia, 85 faths.) the 

 name of a form from the Pacific Ocean. Verrill (1885) saj^s it (incrusting variety) 

 ranges from " 49-906 fathoms; abundant." 



The synonymy has also been complicated on account of the occasional 

 free habit. This variety was first named Sidisia harleei by Gray. Gosse, 

 Holdsworth, and others have regarded it simply as a variety of the typically 

 incrusting Z. couchii. Verrill, too, recognises a free and an incrusting variety 

 of E. americanus, and also for his E. abyssorum ; of this latter he says: "This 

 species generally forms the carcineecia of Parapagurus pilosimanus, but sometimes 

 consists of two or three large obconic polyps arising from a grain of sand" 

 {I. e. 1885, p. 535). 



Norman, however, in referring to this variety, says (1868, p. 319): "Taken 

 abundantly in company with Zoanthus incnistatus, of which I was at one time 

 inclined to consider it a variety ; but more careful examination and dissection has 

 convinced me that there are certain distinctions between the two, besides the fact 

 of Sidisia being a free-living, unattached form. Whether these distinctions are 

 specific or sexual, a careful examination of the living animal must hereafter 

 determine." We have compared microscopically the two varieties, and find them 

 to be essentially similar. 



Incrusting Form. — Coenenchyme incrusting gasteropod shells inhabited by 

 hermit-crabs, the shells being rapidly absorbed and replaced by the coenenchyme 

 which thus forms the carcinsecium. In old specimens the polyps appear to be 

 irregularly arranged ; but on an examination of younger specimens, three series of 

 polyps can be distinguished. In the youngest example we have seen (PI. lviii., 

 fig. 14) there is only a single polyp, which is situated at the apex of a small 

 gasteropod shell, the shell itself being entirely coated by the coenenchyme- 

 The second polyp arises at the oral axis, or hilum, of the shell (fig. 15). 

 A third one usually makes its appearance above the mouth of the shell. 

 We have seen several cases in which the apical polyp is in the act of 

 fission (PI. LVIII., fig. 12). These three polyps form the first series. The second 

 series forms a marginal row which corresponds to the aboral varex of such a shell 

 as Ranella. The third series forms an irregular row between the two former. In 

 no specimen of the very large number we have examined is there a polyp on the 

 under surface of the carcinsecium. The polyjos bend slightly towards the oral or 

 anterior aspect of the cax'cinsecium. In a contracted state the capitulum forms a 



