826 



SYSTEMATIC HISTORY OF THE 12^'FUSOEIA. 



containing these specimens, from wliicli 

 Mr. Bauer's drawings (xvii. 506-509) 

 were made, was found on Brighton 

 beacli. The figures are magnified 100 

 diameters. 



P. prisca, EM. pi. 37. 7. f. 5. This 

 species is found in fiints, and is probably 



the same as the preceding. 



P. ? (jigas, EM. pi. 33. 13. f. 18. Fossil. 

 California. The figure shows a large 

 orbicidar disc, with distant scattered 

 dots, and no suture. 



P. decussata (E.). — Foimd in the chalk 

 marl of ^gina. 



Genus STEPHANOPYXIS (Ehr.).— Enistiiles simple or united into short 

 filaments, in front ^-iew orbicular or oblong, composed of two cellulose valves, 

 each having a crown of teeth, spines, or membrane ; central portion obsolete ; 

 lateral view circular. " This group includes those PyxidiculoB which have 

 tui'gid forms with a cellular sui'face, bearing in the middle of the valves a 

 crown of small teeth, prickles, or a membrane " (Bailey). The fossil species 

 appear simple ; but as recent specimens forming short filaments have been 

 obtained by the Eev. R. Cresswell and Mr. Norman, probably the others also 

 were originally so formed, but, as the crowns prevent the close union of the 

 frustules, they become more easily disconnected. The valves agree in their 

 turgid form, rounded ends, and cellulose structures with Pyxidicula ; but their 

 coronets will easily distinguish them. 



Stephanopyxis Diaclema (E.). — 

 Valves hemispherical, with parallel, 

 straight rows of cellules ; centre of disc 

 depressed, with a circlet of numerous 

 teeth (20 to SO). = Pt/xidicuIa Diadema, 

 KSA. p. 21. Fossil. Virginia ; guano. 

 Diam. 1-576". We have seen two frus- 

 tules connected. 



S. Turris. — Frustides cylindiical, cel- 

 lidose, ends depressed at the centre and 

 fui-nished with a crown of spines or pro- 

 cesses, which are truncate or clavate at 

 their apices ; areolce hexagonal, 7 in 

 •001".= CressivelUa Turris, Grey, in GDC. 

 p. 64, pi. 6. f. 109. In stomach of Ascidia. 

 Teignmouth, Hull, &c. Fossil in guano. 

 We regret being unable to accept the 

 genus Cresswellia, as we believe all the 

 species of Stephanopyxis, when recent, 

 have the frustules connected by their 

 coronets : S. Diadema^ a species closely 

 allied to the present, we have found so 

 united in specimens from guano. This 

 character has probably escaped detection 

 only because in all filamentous forms the 

 fossil frustules are usually separated. 

 The coronets of numerous non-attenuated 

 spines distinguish this species, (v. 74.) 



S. apiculata (E.). — Frustides oblong 

 or subc^dindi'ical, end broadly roimded ; 

 cellules not crowded, arranged in longi- 

 tudinal rows ) centre of disc with a few 



forming 



elongated spines, EM. pi. 19. 13. f. G. 

 America, Europe, guano, ka. 



S. appendiculata (E.). — Frustides in 

 fi'ont view subglobose, coarsely and 

 closely cellidose ; segments with rounded 

 ends, each with an excentric, short, horn- 

 like process. EM. pi. 18. f. 4. Fossil. 

 Virginia. Diam. 1-624". Processes trun- 

 cate, not central j cellules 

 crenated margin. 



S. turglda (Grev.). — Front view cylin- 

 di'ical- oblong ; junction-margins subtrim- 

 cate, with roimded angles and a crown 

 of elongated spines with dilated apices ; 

 areolae 11 in '001. = CressivelUa turqida^ 

 Grev M J. vii. p. 165, pi. 8. f. 14. Cali- 

 fornian guano. This species is nearly 

 related to 8. Turris, but differs in the 

 larger, more truly cylindrical and trun- 

 cate frustules, and in the considerably 

 smaller areolation, Grev. 



S. ferox (Grev.). — Front view oblong ; 

 valves subglobose, campanulate, hispid, 

 with a crown of elongated spines and a 

 thin, hyaline, prominent suture ; areolae 

 large, 5 in -001". = CressivelUa? ferox, 

 Grev M J. vii. p. 166, pi. 8. f. 15, 16. Ca- 

 lifornian guano. The valves are ex- 

 panded at their junction so as to form 

 a sutm-al keel, as in some species of 

 Pyxidicula. (v. 75.) 



Genus XANTHIOPYXIS (Ehr.).— Valves turgid, continuous, entire, non- 

 ceUulose, hispid, setose, or winged. = Pyxidicula olim. Fossil. *' These forms 

 are Pyxidicula with bristles, setse, or wdngs. They have the habit of Xan- 

 thidium and Chtetotyphla, but are bivalvcd and silicious." The true affinity 

 of this genus is doubtfril : we have seen no species which is circular in the 

 lateral view, and consequently consider them misplaced in the Melosirea) ; 



