850 



SYSTEMATIC HISTOKY OF THE USTFUSOHIA. 



Genus PORPEIA (Bailey, MS.). — Frustules simple (?), compressed, each 

 valve with two short obtuse processes, and two internal curved plates which 

 do not extend to the central portion. We give this genus in deference to the 

 opinion of oui' higlily esteemed correspondent the late Professor Bailey, but 

 doubt whether it is sufficiently distinct from Biddulphia. In Porpeia the 

 septa appear like costse incurved at their inner ends. 



Poupeia quadriceps (Bai. MS.). — Pro- 

 cesses with punctated rounded ends, the 

 intermediate margins slightly convex; 

 Literal view narrow, with two constric- 

 tions, and rounded ends. Gulf- stream, 

 (vi. 6.) From drawings by Professor 



Bailey. "At first sight this species 

 suggests a relation to Grammatophora ; 

 but the curved plates rim at right angles 

 to their position in that genus (^. e. not 

 parallel to the division of the fi-ustules, 

 but perpendicular to it)." — B. m lit. 



Genus ZYGOCEROS (Ehr.). — Frustules free, compressed, not concatenated ; 

 each valve with two (apparently) perforated horn-like processes. Although 

 we have retained this genus, yet we think it is very probable that a better 

 knowledge of its species will justify Professor Smith in uniting it with 

 Biddulphia, from which it differs only in its simple frustules. 



Zygocehos Rhomhus (E.). — Frustules 

 turgid, with a smooth or faintly punc- 

 tated central portion; lateral valve rhom- 

 boid with rounded angles, its sm'face 

 having very fine granulated striae. = 

 Biddulphia Rhomhus, SBD. ii. p. 49, 

 pL 45. f. 320; Ro TMS. vii. p. 11, pi. 1. 

 £4. America, Europe, England. ^, valves 

 with one or more median spines, = i)e«- 

 ticella Rhomhus, E. ; Odontella Rhomhus, 

 K. Large ; strias 24 to 26 in 1-1150". 

 Diam. i-720". "Spines submarginal, 

 awl-shaped, abbreviated " (Sm.). 



Z. radiatus (B.). — Frustules large, 

 turgid; lateral valve rhomboid, with 

 rounded angles and radiating series of 

 o-ranides. BSC. vii. Z. Balcena, EM. 

 pi. 35. A. 23. f. 17 ; Bri JMS. vii. p. 181, 

 pi. 9. f. 15. Nova Scotia. "Akin in 

 liabit to Z. Surirella, but larger than 

 Z. Rhomhus. Central zone pimctated " 

 (Ehr.). 



Z. Surirella (E.). — Frustules small; 

 lateral valve lanceolate, with constricted 

 obtuse apices ; surface with transverse 

 granular lines, interrupted by a median 

 longitudinal band. Ro TMS. ii. pi. 6. 

 f. 11, 12. Alive. Europe. Thames, 

 (xi. 50, 51.) Diam. 1-720". Central por- 

 tion smooth, granides of valves more di- 

 stinct than in Z. Rhomhus. Distin- 

 guished by the smooth longitudinal line 

 in a lateral view. 



Z. Bipons (E.). — Frustules laterally 

 lanceolate, with acute ends, and two 

 smooth medi.in constrictions ; granules 

 delicate, not radiant. KSA. p. 139. 

 Bermuda deposit. Diam, 1-384". Angles 

 with small horns. May be kno-s^m by 

 haA ing, in the lateral view, two trans- 

 ^ erse lines. 



Z. stiliger (E.). — Frustules laxly cellu- 

 lose ; valves with double median con- 

 striction of the side; angles produced 

 into long, acute, stiliform horns. KSA. 

 p. 139. Fossil. Bermuda deposit. Diam. 

 1-1152". "Z. stiliger may be a species of 

 Hemiaulus ; but the constrictions resem- 

 ble those of Biddulphia, save that they 

 want the wide apertures of the horns " 

 (Ehr.). 



Z. aust rails (E.). — Frustules smooth ; 

 horns obsolete ; lateral valve turgid- 

 lanceolate, with conspicuous pseudo- 

 openings. KSA. p. 139. Antarctic Sea. 

 Diam. 1-480". 



Z. ?Circinus (B.). — Frustules minutely 

 and decussately punctate ; lateral valves 

 forming truncated cones without pro- 

 cesses, but each having two long, seti- 

 form, bent spines ; lateral view elliptic. 

 BC. vii. pi. 1. £ 19, 20. Fossil. Vir- 

 ginia. Characterized by the conic out- 

 line of the lateral valves, and the absence 

 of nrocesses. 



Z. Navicula, EM. pi. 19. £ 22. Fossil. 

 Greece. Lateral valve oblong, with 

 transverse rows of dots, a transverse 

 smooth median band, and a pseudo- 

 opening at each end. 



Z. paradoxus (E.). — Smooth, laterally 

 linear-oblong with rounded ends. EM. 

 pi. 22. £ 54. = Surirella paradoxa, EM. 

 Caltanisetta, Sicily. 1-576". 



Z. Siculus (E.). — Smooth, linear ; 

 laterally rhomboid, with obtuse ends. 

 EM. pf. 22. £ 53. = Surirella 7'homhoidea, 

 EM. Fossil. Sicily. 1-744". 



Z. Mohiliensis (B.). — Frustules qua- 

 drangular, thin, delicately punctate; 

 valves with slender, tapering lateral 

 processes, and two slight intermediate 



