478 MR. a. R. VINE ON THE POLYZOA OF 



(Terr. Crt't. p. 867) shows how very common the D'mstoporo'. with 

 simple non-characteristic zooecia are. It is, indeed, as Dr. Pergens 

 ver)' wiselv suggested in a recent letter, a most uni^ntisfactory group 

 to deal with and distinguish. I have been, however, so far very suc- 

 cessful with the Ived-Chalk species ; but duplicates of all the forms 

 indicated in tlie text are by no means easy to get, even out of the 

 abundant series submitted to me. 



Habitat. On Terebratula hiplicata. Fossil No. 27. 



Horizon. Eed Chalk, Hunstanton. 



28. DiASTOPORA Jessoni, sp. nov. (Plate XIX. figs. 12 r^, 12 h.) 



Zoarium adnate, without marginal lamina or partially formed 

 cells on the edge, orbicular. Zooecia : originating cells central, verj' 

 short and compressed ; radial cells either linear or slightly oblique 

 where the lines reach the edge from the centre; these linear series 

 widen out towards the margin, so as to admit an intermediary 

 series between the radii, by which the zoarium is enlarged ; zooecia, 

 either elongated tubes, of about the same diameter throughout, or 

 flask-like, narrow towards the proximal and bulging at the middle 

 or at the distal extremities ; orifice circular or oval (?), raised, 

 with very thin peristomes ; surface of cells punctate in fine and 

 closely transverse series, which give a rugose appearance to the 

 zooecia if only examined under a low power of the microscope, or by 

 the hand-lens. Closure-cells occasional, with very finely perfo- 

 rated " opercula," which form a slightly rounded covering over the 

 orifice of the cells. These closure-cells are probably equal to the 

 ovicells in other species ; anyhow they are very characteristic in 

 certain species of Diastopora in the Red Chalk. 



Habitat. On Terebratula bipJicata, Fossil No. 25 ; aud on Nautilus 

 albensis, d'Orb., in Mr. C. D. Sherborn's collection. 



Horizon. Red Chalk, Hunstanton. 



The general outline of Diastopoi^i Jessoni is similar to that of 

 I), f/racilis (d'Orb. pi. 635. fig. 9), and it is about the same, size 

 (natural) of fig, 8 on the same plate. In d'Orbigny's text (Terr. 

 Cret. p. 864) I find that the author includes under Berenicea gracilis., 

 d'Orb., both D. intermedia and D. vassiacensis, d'Orb., of the same 

 plate ; in any case it would be impossible to place the Red-Chalk 

 form under any of these specific names, whether we regard them 

 as synonyms of ]\filne Edwards's D. cjracilis or not. The next 

 species, somewhat similar as regards the flask-like cells, is the 

 Berenicea pilosa, Novak (Bibliogr. 34, pi. iv. fig, 10, only) ; besides 

 these, I know of no other species with which I can compare 

 D. Jessoni. 



I have already dedicated a Proboscina to Mr, Jcsson, so as to 

 connect his name with these Red-Chalk fossils, and, in my remarks 

 on Proboscina Jessoni, I made reference to the small special col- 

 lection which came after the larger mass of fossils had been placed 

 in my hands : and the fossils to which P. Jessoni and D. Je^^soni 

 were adherent w^re in this parcel. Mr. Jesson has, therefore, a 

 double claim to remembrance in the distribution of specific names. 



