842 



SYSTEMATIC HISTORY OP THE INETJSORIA. 



Arachnoidiscus ornatus (E.). — Disc 

 having its radiating lines connected by 

 concentric ones. = ITemiptychus ornatus, 

 EB. 1848, p. 7 ; Arachnoidiscus ornatus, 

 EB. 1849, p. 64 ; Ar TM. vi. p. 16 ; 

 A. JaponicKS, Shadbolt; A, Nicoharicus, 

 EM. pi. 36. f. 35 (according to Arnott). 

 Africa, West Coast of America, Nicobar 

 Islands, (xv. 18-21.) In deference to the 

 opinion of Prof. Arnott, we liave united 

 A. Nicoharicus to this species ; but it is 

 desirable to examine specimens from the 

 original stations. Ehrenberg describes 

 all the radiating lines in his A. ornatus as 

 equal ; but he figures A. Nicoharicus with 

 two sets of shorter, marginal, interme- 

 diate ones. Our specimens, in this re- 

 spect, agTee with A. Nicoharicus, but 

 have around the umbilicus a circlet of 

 close, short, radiant, oblong lines, which 

 are wanting in Ehrenberg's figure. The 

 granules, too, are apparently larger in 

 our specimens. The lines connecting the 

 radiating ones often anastomose. 



A. Ehrenbergii (Bailey). — Disc with 

 numerous, moniliform, concentric circles 

 of large pearly granules, the circle next 

 the umbilicus formed of short lines; 

 radiating lines wdth two series of shorter 

 ones between. = ^. Ehrenherqii, EB.1849, 

 p. 64 ; SD. i. p. 26, pi. 31. f. 256. Eecent, 

 Coast of Oregon and California; fossil, 

 Monterey and California. A. Ekren- 

 hergii is easily distinguished from A. 



ornatus by the absence of concentric 

 lines. It is more hyaline, and the gra- 

 nules far larger and more conspicuous. 

 All the circles are compact, and, except 

 the two inner ones, have the granules 

 slightlv quadrate, and their relative di- 

 stances somewhat irregular. The second- 

 ary rays are sometimes half the length 

 of the principal ones ; the third series is 

 simplv marginal. 



A. hidicus, EM. pi. 36. f. 34. India. 

 We have seen neither specimen nor de- 

 scription of this species. Ehrenberg's 

 figm-e represents the disc with numerous, 

 concentric, moniliform circles of pearly 

 granules. The granules are distant in 

 the first and third from the umbilical 

 space ; in all the others they are dense. 

 Professor Arnott (perhaps rightly) imites 

 A. Indicus to A. JSJirenhergii ; but we 

 have thought proper to keep them sepa- 

 rate for the present, in order to direct 

 more attention to them, because Ehren- 

 berg's figm*e of A. Indicus differs in some 

 respects from A. Ehrenhergii. In this 

 species there is no linear series roimd 

 the umbilicus, the third circle has distant 

 granules, all the granules are orbicular, 

 there is only one series of shorter rays 

 interposed between the long ones, and 

 these are connected by an imdulated 

 line, giving the inner margin of the rim 

 a scolloped appearance. In all these 

 respects it difiers from A. Ehrenhergii. 



Genus PEHITHYEA (Ehr.). — Characters unknown to us. According to 

 Ehrenberg's figures, it seems to differ fi^om Heterostephania by its larger 

 tubercles. 



Perithyba denaria, EM. pi. 35 a. 9. 

 f. 5. = Coscinodiscus radiatits, var., Wal- 



lich, TMS. 



pi. 2. f. 22 ? Ganges. 



Disc with radiating series of minute 

 puncta, ten intramarginal tubercles, a 



rather broad, smooth rim, and no umbi- 

 licus, (viii. 19.) 



P. quaternaria, EM. pi. 35 a. 9. f. 6. 

 Ganges. A variety of the preceding, 

 with only foiu' tubercles. 



FAMILY IX.— EUPODISCE^. 



Frustiiles simple, free, disciform ; lateral surfaces furnished with processes. 

 The Eupodiscese may be regarded as connecting the Coscinodisceae with the 

 Biddulphiese. They agree with the former in theii' discoid fnistules and with 

 the latter in having processes on the lateral surfaces. These processes, how- 

 ever, must not be confounded with the spines or teeth which occiu' in some 

 of the Coscinodisceae. It is sometimes difiicult to decide whether the discs 

 really have processes or only pseudo-nodules, since, from their circular out- 

 line and hyaline texture, free from cellules, both these appear like orifices 

 unless seen in profile, and perhaps Aetinocyclus would be more correctly 

 placed in this family than with the Coscinodisceae. 



Genus EUPODISCUS (Ehr.).— Frustides disciform ; disc cellulose or gra- 

 nulate, furnished with submarginal circular prominences. = Tripodiscus, Tetra- 



