356 G. E. TINE ON THE FAMILY DIASTOPOEIDiE. 



26. A Review of the Family Diastopoeid^ for the jpurpose of 

 Classification. Ey Geoege Robeet Yine, Esq. (Cominuni- 

 cated by Prof. Duncan, M. B. Lond., F.R.S., P.G.S.) (Read 

 May 12, 1880.) 



[Plate XIII.] 



The DiastoporidsD are a group of adherent Polyzoa belonging to the 

 suborder Cyclostomata. Busk defines the generic characters thus : — 

 "Zoarium crustaceous or foliaceous, discoid or indefinite in outline; 

 adnate and sessile, or pedunculate and erect ; no cancelli " *. This 

 restricted definition limits the group to almost a single genus ; for 

 the Mesenteripora of Blainville is the only other genus classed by 

 Smitt and Busk among Diastoporidae, and the non- cancellated surface 

 separates this small family from the Discoporellidse. 



In this review of the recent and fossil Diastoporidae we must bear 

 in mind the restriction formulated by Busk, because as we go back- 

 ward in time the necessity of this caution will be apparent. The 

 family was never prolific either generically or specifically ; but in 

 nearly all the seas, from the Lower-Silurian era to the present, re- 

 presentatives of the family are generally found in deep-sea deposits. 

 Their geographical range now is chiefly northern ; and their bathy- 

 metrical range in the past was as variable as now. 



In his definition of the genus Diastopora^ Busk says : — " Zoarium 

 adnate, discoid or flabelliform, centric or excentric, margin entire or 

 lobed ; cells towards the centre wholly immersed, usually suberect, 

 and partially free towards the margin ; mouth elliptical or subor- 

 bicular, horizontal or oblique "f. As there is no typical species in 

 which the whole of these characters are j^reserved, we are compelled 

 to seek them in the five species catalogued as recent and fossil by 

 Busk. But there are specific characters not embraced in the generic 

 definition, to which I wish to direct attention. In D. simplex the 

 surface is coarsely punctate, and there are no " adventitious tubules." 

 In D. obelia, Johnst., the surface is finely punctate, and a small 

 " adventitious tubule rises from the back of some of the cells." In 

 D. patina, Lamk., the central cells are immersed and usually closed, 

 whilst the marginal ones are erect and open ; and in D. congesta, 

 D'Orb., the cells are decumbent, the surface is spotted, and a secon- 

 dary disk arises from the surface of the primary one. In pi. xxxiv. 

 of the ' Cyclostomata,' Busk gives a figure of D. sarniensis, IN'orman, 

 but no descriptive text. Norman, however, claims for this species a 

 separate identity; but the most characteristic feature is its size, 

 " and here and there among the open-mouthed cell-tubes there 

 occurs a tube which, instead of being open, is closed above with a 

 little cup, from one side of the centre of which rises an umbonal- 

 like process, which is perforated at the apex. Probably these organs 



* Mus. Cat., pt. iii. Cyclostomata, p. 27. t Ibid. p. 28. 



