864 



SYSTEMATIC HISTOKY OF THE rNFUSORIA. 



Genus GONIOTHECIUM (E.). — Friistules simple, having a central con- 

 striction or furrow ; each end abruptly attenuate and truncate, so as to assume 

 an angular figure. Fossil. Like other genera in this family, this is an un- 

 satisfactorj^ genus. The frustules are described as C3^1indrical ; but we believe 

 that most, if not all of them, are oval when viewed laterally. Mr. Brightwell 

 makes the following remarks on eight of Ehrenberg's species : — " The two 

 largest and most common are G, Bogersii and 6r. OdonteUa ; and we think it 

 probable these will tui^n out, if discovered in a recent or living state, to be 

 Chajtoceri. Of the remaining six species, we are led to conclude, from the 

 discovery of the Breydon species, that two of them belong to the genus 

 Chaetoceros, and are, when living, filamentous. They are G. Gastridium, of 

 which we have found many specimens with the horns perfect, and G. crenatum. 

 A figure of a frustule of this species is given in the ' Microgeologie ' of Eh ^en- 

 berg, and it can scarcely be distinguished from the frustules of the Breydon 

 species. 6r. Tiispidum and G. dklymimi scarcely appear to differ fi^om some of 

 the smaller frustules of the Breydon sj^ecies. G. Navicula and G. barhatum 

 are clearly allied to G. crenatum, or our Breydon species." The species differ 

 in form, and sometimes do not correspond "with the generic character. G. 

 Gastridium (E.) is proved by Mi\ Brightwell's discovery of its awns to be a 

 species of Chaetoceros. 



GoNiOTHECiUM OdonteUa (E.). — 

 Valves binate, smooth, conjoined by a 

 central process, and by their connivent 

 apices, so as to form on each side a 

 large oblong apertm-e, constricted at its 

 middle ; margin undulate. EM. pi. 33. 15. 

 f. 16 ; KSA. p. 23 ; Bri JMS. v. pi. 7. 

 f. 47, 48. Virginia. Diam. 1-480" to 

 1-276". Distinguished by its large size 

 and undulated margin, the central un 



projection (connecting process), and 

 agrees but badly with the specific cha- 

 racter. 



G. hispidum (E.). — Frustules semi- 

 lunate, hispid, with an imibo at the 

 centre of inner margin. EM. pi. 18. 

 f. 107 ; KSA, p. 23. Virginia. 



G. Navicula (E.). — Frustules small, 

 smooth, with a linear produced central 

 portion and a turgid or inflated valve on 



dulation forming an umbo ; lateral view } each side. EM. pi. 18. f. 105 ; KSA. p. 24, 



oval. (^^. 29.) 



G. Rogersii (E.). — Valves binate, 

 smooth, conjoined by a broad central 

 process, often with connivent apices, 

 forming suborbicular apertm'es ; margin 

 undulate. EM. pi. 18. f. 92, 93 ; KSA. 

 p. 23. Virginia. Diam. 1-588". Smaller 

 than G. OdonteUa ; " valves dorsally sub- 

 quadrate, angular, with three whorls, 

 laterally elliptic-oblong, with two or 

 three median circles; " central undulation 

 unibonate. Mr. Brightwell's figures are 

 more irregular, and do not correspond so 

 accurately with the definition. 



G. ohtusum (E.). — Valves smooth, in- 

 flated, with three rounded lobes ; central 

 or constricted portion forming a narrow 

 band. EM. pi. 18. f. 95 ; KSA. p. 23. 

 Virginia. Diam. 1-696". 



G. monodon (E.). — Valves binate, 

 smooth, not contiguous, each linear- 

 oblong, truncate at each end ; outer side 

 uniformlv straight, the inner with a 

 median tuberositv. EM. pi. 18. f. 97 ; 

 KSA. p. 23. Virginia, Cahfomia. Ehr- 

 enberg's figures represent a canoe-shaped 

 valve, the outer margin convex, the 

 inner with incurved ends and a central 



Virginia. In this species the central 

 portion projects beyond the lateral valves, 

 instead of being constricted. 



G. didi/mwn (E.). — Binate, smooth, 

 transversely oblong, obtuse ; one side 

 emarginate at the centre, the other with 

 two tubercles. EM. pi. 18. f. 104; KSA. 

 p. 23. Virginia. Diam. 1-1200". Ehr- 

 enberg's figure shows two imequal valves 

 without any interstitial portion, each 

 valve with two rounded lobes. It re- 

 sembles a hornless state of Dicladia, 

 except that it wants the central portion. 

 ^ G. harhatum, EM. pi. 18. f 106. Vh- 

 ginia. Ehrenberg's figm'e has a narrow- 

 linear, longly produced central portion 

 and two unequal turgid valves — the 

 smaller smooth, the larger conic with a 

 tuft of hairs at its apex. 



G. crenatum, EM. pi. 39. 3. f. 74. Ehr- 

 enberg's figure is semilunate, with a 

 neck-like truncated cone on its inner 

 side. This species, except in being 

 smooth, exactly resembles Mr. Bright- 

 well's figures of the internal frustules of 

 ChcBtoccros Wighamii, and doubtless be- 

 longs either to that or to an allied species 

 of Chretoceros. (xv. 10.) 



