General History of the Marine Polyzoa. 247 



whether there is any valid ground for separating them from 

 it. The disjunct cells and the more or less decumbent habit are 

 the only characters that could be relied on as distinctive. The 

 fiist and more important of these would seem to have little 

 real significance, for it occurs as an occasional condition in 

 species the cells of which are normally continuous. We have 

 an instance of this in the disjunct form of the well-known 

 Microporella Malusii, described in this paper. The second 

 of the characters referred to is absolutely unimportant. Pro- 

 bably the natural relationships would be best represented by 

 ranking; the true forms of Diachoris as a subsection of the 

 genus Bugula. 



One of the species hitherto referred to it, merely because its 

 cells are disjunct, and without any regard to its other^ and 

 much more important characters, is the Eschara patellar ia of 

 Moll (=Diachoris simplex, Heller), which is an undoubted 

 Membranipora. The short connecting processes between the 

 cells vary in number; there are sometimes six of them, some- 

 times (as in the form multijuncta of Waters) nearly a dozen. 

 So far as this portion of the structure is concerned, there 

 is no essential difference between Eschara patellaria axiASchizo- 

 porella argentea, mihi (noticed in this paper), or the disjunct 

 form of Microporella Malusii, before referred to. 



Busk, in his ' Catalogue,' places the genus Diachoris in 

 the family Flustrida?, and holds to this arrangement in his 

 1 Challenger ' monograph ; but, in my judgment, it has much 

 closer affinity with the Bicellarmke. The purely membranous, 

 more or less boat-shaped cell agrees exactly with that of 

 Bugula, whilst the articulated avicularium is an essentially 

 Bicellarian character. In the Flustrine group this appendage 

 exhibits a much humbler structure and the simplest primary 

 forms prevail. 



I add a list of the known species and varieties of Diachoris 

 as just defined : — 

 Diachoris crotali, Busk. Diachoris armata, Seller. 



Magellanica, Busk (=D. spinigera, MacGiUiyray. 



Buskei Heller). decumbens, Mac G Mi way*. 



f v ar. distans,i?tt«ft (' dial- Buskiana, Huttmi. 



lenger ' Monograph). bilaminata, Hi neks. 



inermis, Busk. ' distans, Hincks. 



costata, Busk. intermedia, Hincks. 



hirtissima, Heller (Chaunosia, elongata, Hincks. 



Busk). quadricornuta, Hincks. 



, form robusta, Hincks. 



* MacGillivray places this form under Beania; but the presence of 

 avicularia and the mode in which the cells are united, which differs 

 • ssentially from that which is met with in the latter genus, seem to con- 

 nect it with Diachoris. 



