HARDWICKE'S SCIENCE-GOSSIP. 



145 



THE DIASTOPORID^ : OR THE NATURAL HISTORY 



OF A FAMILY TYPE. 



By GEORC'.E ROBERT VINE. 



\Continued/ro7n page 83.] 



H E family Diasto- 

 poridse is defined 

 by Busk, " Zo- 

 arium* cnistaceous 

 or foliaceous, dis- 

 coid or indefinite 

 in outline, adnate 

 and sessile, or pe- 

 dunculate, or 

 erect ; no cancel- 

 li ;" and the genus 

 Diastopora is de- 

 fined, " Zoarium 

 adnate, discoid or 

 flabelliform, cen- 

 tric or excentric ; 

 margin entire or 

 lobed; cells toward 

 the centre, wholly 

 immersed, usually 

 suberect, and par- 

 tially free towards the margin ; mouth elliptical or 

 suborbicular, horizontal or oblique."t 



The generic meaning of this term is that the cells 

 are separated, or that there is a small intervening 

 space between the pores. There are no " cancelli," 

 or smaller openings in these spaces, so that the family 

 is distinct on this account from another, the Disco- 

 porellid?e, in which the intermediate spaces are can- 

 cellated or porous. The Discoporellidje range from 

 the Arctic seas to as far south as Australia and 

 Tasmania. 



All the Diastoporse known to us at the present time 

 as living in our seas are five species, and the geo- 

 graphical range of these is entirely northern. Dia- 

 stopora simplex, the D. suborbicular is of Hincks, is 

 distinguished by its papyraceous character, and also 

 by its irregular growth ; the cells are deeply immersed, 

 and sometimes the mouths of the cells are nearly 



* Polyzoary of previous authors, 

 t " Cyclostomata," pp. 27, 28. 



even with the surface. This species ranges in space 

 from the Arctic sea to South Devon, where it is very 

 abundant, and the habitat is from shallow to deep 

 water. It is often found on shells and stones, and 

 the dredge has brought up specimens at from 1 10 to 

 145 fathoms. Mr. ^Yaters, in his "Naples Bryozoa,"* 

 obtained specimens at from two to six fathoms. This 

 species ranges in time from the present seas to the 

 Miocene of Austria, and a critical study of the 

 varieties will reveal the fact that it will not submit 

 to an entirely arbitrary diagnosis. Or, in other 

 words, between the recent and the fossil specimens, 

 there is a slight divergency from the type, as found 

 in the British Museum Catalogue, though by the 

 laws of precedence the crag D. simplex ought to be 

 the type. 



In the Crag Polyzoa Mr. Busk says that the "tubes 

 are not flattened in front," but in the Cyclostomata 

 they are merely stated to be " deeply and entirely 

 immersed." The general aspect of the species is that 

 the zoarium is orbicular, or nearly so, and that the 

 cells are slender and very thickly or coarsely punctate. 

 These in some parts of the colony are nearly wholly 

 immersed, and sometimes partially free, and a refer- 

 ence to Busk's figuresf will show this double char- 

 acter, more particularly as representative of the crag 

 specimens. The synonyms of this species are some- 

 what limited, derived chiefly from special character- 

 istics of the specimens examined. The name was 

 originally given by Mr. Busk in his " Crag Polyzoa," 

 but as the species have been associated doubtfully 

 with D. obelia, Johnston, and D. Jlabellum, Reuss, 

 Mr. Hincks has redescribed and rechristened it as 

 D. siiborbiadaris. 



Another of Mr. Busk's species is the D. obelia. 

 Johnston. In this the zoarium is adnate and usually 

 slightly raised in the middle, or umbilicate, orbicular, 

 or irregular in outline ; cells produced and partially 

 free and erect. The leading characteristic is, however, 



• Ann. Mag. Nat. Hist., 1879. 

 t 3 & 4 PI. 29, " Cyclostomata." 



No. 21 r.— July 1882. 



