ADDENDA. 



939 



gin; granules radiating, not reaclaing 

 the centre, 9 in '001" j smooth round the 

 base of the processes. Deposit from 

 Nottingham, below Maiyland, which 

 seems to be identical with the Bermuda 

 tripoli, and contains several forms pecu- 

 liar to that deposit" (Norman in litt). 



A. Barhadensis (Ralfs, n.s.). — Disc 

 large, hyaline, very minutel}' punctated, 

 with small umbilicus, (8) intramarginal 

 roundish processes, and faint connecting 

 lines. Barbadoes deposit. Distinguished 

 by its very obscure puncta. The rather 

 large processes, when nearly out of focus, 

 appear to have a central dot. 



Teiceratium crenatum (Kitton, MS.). 

 — Sides rounded, margin crenate ; gra- 

 nules radiating from the pseudo-nodule, 

 distinct at the margin, but less con- 

 spicuous as they approach the centre. = 

 Discoplea undulata, EM. pi. 33. 18. f. 3. 

 Nottingham deposit. The presence of 

 the pseudo-nodule shows it to be an ally 

 of T. Brightwellii ; but the nearly orbicu- 

 lar outline and crenate margin distin- 

 guish it from that species. The frag- 



ment figm'ed by Ehrenberg we have no 

 doubt is identical with this form. 



T. Bowerhankiana (Ralfs). — Valves 

 with two concentric circles, radiating 

 lines between the circles, distinctly punc- 

 tated angles, and blank or indistinctly 

 punctated centre. Barbadoes deposit. 

 The large valve has nearly straight sides, 

 and obtuse angles; it is divided into 

 three parts by two suture-like circles, 

 the outer one with a border of bead-like 

 dots, which are most evident nearest the 

 sides ; the lines between the circles are 

 abbreviated, only one on each side reach- 

 ing the inner circle. 



Grasped ODisc us Barhadensis (Ralfs, 

 n. s.). — ^Border very broad, its diameter 

 greater than that of the centre ; cellules 

 of centre very minute, those of border 

 larger and arranged in cun^ed, decussat- 

 ing lines. Barbadoes deposit. Disc 

 about the size of C. Coscinodiscus, but 

 with a much smaller centre. It differs 

 from both that species and C. microdiscus 

 in having the cellules of the border in 

 cm'ved series. 



Substitute the following descriptions for the notices of Craspedodiscus Stella 

 and C. FranUini at p. 832 :— 



C. ? Stella (E.). — Valves hemispherical, 

 with a very broad, smooth, obsoletely 

 radiated limb, and a small, finely cellu- 

 lose centre, having an irregular margin ; 

 rays 12, irregular. EB. 1855, p. 238 ; E 

 M. pi. 35 B. B. 4. f. 11. North America. 

 On account of its rays, this form may be 

 the type of a new genus ; but they were 

 distinct only in a single specimen, whilst 

 in the greater number scarcely a trace of 



them could be detected. It approaches 

 to the characters of Symbolophora. 



C. Franklini (E.). — Disc tm-gid, with 

 a deciduous, broad, hyaline, smooth 

 marginal limb, and a very tine punctated 

 (yellowish) centre, having an irregular 

 margin ; centre and limb of nearlv the 

 same diameter, ERBA. 1853, p." 626; 

 EM. pi. 35 A. 23. f. 6. Assistance Bay. 

 Akin to Coscinodiscus disciger. 



To C. semiplanus (Bri.), add : — 



This Diatom, which is not uncommon 

 in the Barbadoes deposit, is no doubt 

 incorrectly placed in this genus. In our 

 opinion it is closely allied to Astero- 

 lampra, and should either be united to 

 that genus, or a new genus formed to 



To C. marginatus (Bri.), add : — 



We consider that this Diatom also is 

 wrono^ly referred to Craspedodiscus, and, 

 notwithstanding its large punctated 

 centre, is really more allied to Astero- 

 lampra, — its marginal compartments, 

 however, being extremely minute. In 

 the Barbadoes deposit we find discs 

 sometimes (as in Asterolampra) without 

 any umbilical cellides, and sometimes 

 with a larffe cellulose centre, and these 



include this and other allied discs asso- 

 ciated together in the deposit. Mr. 

 Brightwell's specimen must have been 

 imperfect, since we find the radiating 

 lines invariably correspond in nmnber 

 with the marginal compartments. 



extremes so connected by intermediate 

 states as to make it doubtful whether 

 the cellulose centre is available even 

 as a specific distinction. We hope Dr. 

 GreviUe, who has paid much attention 

 to these forms, waU soon publish a 

 monograph of them in continuation of 

 his former admirable paper on Astero- 

 lampra. 



