OP THE CYMBELLE^. 



883 



obtuse ends; outer portions slender, 

 arcuate, with slightly concave renter, 

 acute ends, and about 22 conspicuous 

 transverse sti'iae in -OOl". GDC. p. 39, 

 pi. 4. f. 68. Scotland. 



4* Frustules neither constricted at the 

 middle nor rostrcde at the ends ; nodules 

 roundish, 



A. ovaUs (K.). — Frustides turgid, oval, 

 with broadly rounded or truncate ends ; 

 outer portion of valves canoe-shaped, 

 with 24 distinct moniliforni strife in 

 •001" ; connecting zone wdth very fine 

 longitudinal lines. KB. p. 107, t. 5. 

 f. 35, 39. = Navicula Amphora, E Inf. 

 t. 14. f. 3. Fresh water, frequent. Eu- 

 rope, Afi-ica. (vn. 56; IX. 153.) Large. 

 1-456" to 1-120". 



A. Lihyca (E,). — Frustules oval, with 

 wdth broadly rounded or truncate ends ; 

 lateral view semilimate, with very con- 

 vex dorsimi, obtuse ends, and slightly 

 concave venter. EA. t. 3, 1. f. 42 ; EM. 

 many figures. Apparently the most 

 common species, since Ehrenberg gives 

 upwards of 100 habitats for it in Em^ope, 

 Asia, Africa, and America. Lough 

 Mourne deposit. (xii. 38.) We are 

 unable to distinguish this form from A. 

 ovalis, and probably these have been 

 confounded ; we believe they are in 

 SBD., because there no species but A. 

 oralis is noticed as occm-ring in the 

 Lough Mom-ne deposit, whilst Ehren- 

 berg only mentions this species as found 

 in it. Ehrenberg's figures and descrip- 

 tion do not enable us to decide ; for the 

 latter is too indefinite, and the former 

 vary so much as apparently to belong to 

 more than one species. Almost the only 

 characters the figures have in common 

 are the oval form and striated valves. 

 The median line is either concave, 

 straight, or produced at the nodule ; and 

 the connecting zone is figured sometimes 

 smooth, and sometimes with longitudinal 

 lines. 



A. peUucida (Greg.). — Frustules very 

 Hyaline, oval, with broadly rounded 

 ends; outer portions of valves canoe- 

 shaped, with about 30 very delicate striae 

 in -001". GDC. p. 41, pi. 4. f. 73. Scot- 

 land. Resembles A. ovalis in form, but 

 differs in its marine habitat, veryhj^aline 

 aspect, and singular delicacy of the striae. 

 The latter characters distinguish it also 

 from A. incurva, Greg. 



A. truncata (Greg.). — Frustules barrel- 

 shaped, with truncate ends ; outer por- 

 tions of valves canoe-shaped, striated ; 

 dorsum with longitudinal series of short 



transverse striae. GDC. p. 43, pi. 6. 

 f. 77. Scotland. Large. 



A. lineolata (E.). — Frustules tm'gid, 



elliptic-oblong, wdth truncate apices, 



strong longitudinal marginal lines, and 



! very fine ones in the connecting zone. E 



' Inf. t. 14. f. 14; EM. pi. 13. 1. f. 19 ; Rab 



! D. pi. 9. f. 9, 10. Fresh water. Europe, 



I Africa, America. 1-480" to 1-140". The 



I figm'es referred to represent the frustule 



I as large, barrel-shaped, wdth canoe- 



j shaped outer portions. 



I A. Grec/orii. — Frustules barrel-shaped; 



outer portions canoe-shaped, with about 



34 transverse striae in -001" ; dorsum wdth 



longitudinal series of short transverse 



striae. =^. quadrata, GDC. p. 49, pi. 6. 



f. 85. Scotland. Ends trimcate. 



A. Grecilliana (Greg.). — Frustules 

 broad, linear, oblong or barrel-shaped; 

 outer portions canoe-shaped, with from 

 28 to 34 distinct, moniliforni transverse 

 striae in -001" ; dorsum with longitudinal 

 series of transverse striae. GTM. v. pi. 1. 

 f. 36 ; GDC. p. 50, pi. 5. f. 89. = ^. com- 

 plexa, GDC. p. 51, pi. 5. f 90 ; A. fasciata, 

 GDC. p. 51, pi. 5. f. 91. Scotland." Large ; 

 ends trimcate. 



A. sulcata (Breb.). — Frustules hyaline, 

 oblong or elliptic-oblong, wdth trimcate 

 ends ; outer portions canoe-shaped, with 

 38 transverse striae in -001" ; dorsum 

 with longitudinal series of transverse 

 striae. BD. pi. 18. f. 8 ; GDC. p. 51, 

 pi. 5. f. 92. France, Britain. Large ; 

 differs from A. costata in its not produced 

 but truncate apices, Breb. 



A. rohusta (Greg.). — Frustules broadly 

 oval, with rounded ends and canoe- 

 shaped outer portions ; transverse striae 

 distinct, moniliforni, 16 in -001". GDC. 

 p. 44, pi. 5. f. 79. Scotland. Large ; 

 conspicuous from its size and stoutness. 



A. Proteus (Greg.). — Frustules barrel- 

 shaped or oblong ; outer portions canoe- 

 shaped, wdth 22 finely moniliforni trans- 

 verse stri^ in -001". GDC. p. 46, pL 5. 

 f. 81. Scotland. Large, with truncate 

 apices. Varies much in form and length. 

 A. Arcus (Greg.). — Frustules barrel- 

 shaped; outer portions narrow, canoe- 

 shaped, with 16 to 18 coarsely monili- 

 form striae in -001" ; dorsum wath longi- 

 tudinal series of moniliform transverse 

 stria3. GMJ. iii. pi. 4. f. 4 ; TM. v. pi. 1. 

 f. 37 ; GDC. p. 50, pi. 5. f. 88. Scotland. 

 Large, with truncate ends. The frustule 

 has the form of a barrel, with ribs and 

 bars. It is distinguished from A. Gre- 

 villiana by its coarsely moniliform striae. 

 Detached segments resemble in form a 

 strung bow wdth rostrate apices. 

 3l2 



