MUSEUM OF COMPARATIVE ZOOLOGY. 13 



Acanella Geay (emended). 

 Acanella Gkay, Cat. Lithophytes Brit. Mus., 1870, p. 16. 



Coral either simple or variously branched. Axis with long calcareous joints 

 and very short horny ones. The branches, when they exist, arise from the horny 

 joints, either singly or two or more together, sometimes forming whorls. Coen- 

 enchyma very thin, containing, more or less abundantly, elongated fusiform 

 spicula, usually of large size. Calicles large, elongated, composed of large, fusi- 

 form spicula, often obliquely arranged; the margin is armed by about eight long, 

 spine-like, projecting acute spicula. Tentacles stiffened by abundant spicula. 

 Base, in most cases, divided into large, flat, palmate lobes, which descend into 

 the mud and serve as supporting roots or anchors. 



This genus, as established by Gray, for A. arbuscula Johnson, had as one of 

 its most prominent characters the verticillate arrangement of the branches. 

 The discovery of several closely allied species without this peculiarity, one of 

 them being entirely simple, shows that the mode of branching, as in most 

 other genera of Gorgonacea, is only a specific character. 



The relation of this genus to Isidella Gray is still doubtful, for the nature of 

 the coenenchyma and calicles of the type-species of the latter was unknown to 

 Gray. Indeed, the precise species which he had in view is very doubtful, 

 although he referred it to I. elongata Esper, a species that had never been 

 properly described, and which could not be positively identified, as it was 

 based on the axis only. The species described under the same name by 

 Philippi is probably a distinct species, having elongated calicles, with long 

 projecting spicula, as in Acanella. 



I have hitherto referred to /. elongata, a species procured at Naples, many 

 years ago, by Professor J. D. Dana, and of which several specimens, consisting 

 of the axis alone, are in the Museum of Yale College. So far as the axis 

 shows, these migtt belong either to Acanella or to Lepidisis, or to a genus dis- 

 tinct from either. 



Koch has described a species, perhaps the same, under the name of Isis 

 Neapolitana, which may be the species intended by Gray as the type of Isi- 

 della, and which is apparently the same as my /. elongata from Naples. In 

 this species the calicles are not furnished with the projecting spicula, so con- 

 spicuous in Acanella and Lepidisis. The corresponding spicula are present, 

 however, according to the figures given by Koch, as fusiform spicula, larger 

 than the others, but not projecting beyond the margins of the elongated cal- 

 icles. The coenenchyma is thin, and contains small fusiform spicula. This 

 species is, therefore, closely allied to Acanella, the principal diff'erence being 

 the less development of the marginal spines of the calicles. Possibly this may 

 be the species called Isidella elongata by Gray, but it would be difiicult to prove 

 it. Therefore it might be best to reject the name, Isidella, as not recognizably 

 established. Otherwise it might be restricted to such species as /. Neapolitana 

 and /. horealis (= Mopsea horealis G. O. Sars), in which the marginal spines are 

 not much developed and do not project. 



