OF THE NAYICULEiE. 



919 



pi. 21. f. 203. Marine. Biitaiu. 1-90" ; 

 colour pale straw ; front view narrow 

 linear-lanceolatO; with obtuse apices. 



3 t A'alves lanceolate, with longitudinal 

 and transverse strife. 



P. obtusatum (Sullivant). — Oblong- 

 lanceolate, slightly sigmoid, with obtuse 

 apices ; -0025" ; striae transverse and 

 longitudinal, 56 in -001". Silliman's J. 

 xxvii. p. 251. Fresh water. United 

 States. A very small species, remark- 

 able for the obtuse ends. It may be a 

 CoUetonema, but we have not observed 

 it in gelatinous envelopes. 



P. Spenceri (Quekett, S.). — Small, 

 lanceolate, moderately flexed, gradually 

 tapering to the obtuse apices; median 

 line central ; striae verv tine, transverse 

 50 in -001", longitudinal 55 in -001". 

 SD. i. p. 68, pi. 22. f. 2l^. = Nai'icula 

 Spenceri, Quekett. Fresh water. America, 

 Europe. Colour pale brown. 1-270". 



P. Parkeri (Harrison). — Lanceolate, 

 considerably flexed, apices produced, 

 median line central ; striae transverse, 

 55 to 60 in -001"; longitudinal striae 

 faint ; colom' pale yellow. Lincoln- 

 shire. MJ, viii. p. 105. 



P. IVormleyii (Sidlivant). — Lance- 

 olate, conspicuously sigmoid, suddenly 

 attenuated into acute apices ; "003" ; 

 striae, longitudinal and transverse, 52 in 

 •001". Silliman's J. xxvii. p. 251. Fresh 

 water. United States. Resembles P. 

 Spenceri, but is a smaller species, more 

 evidently sigmoid, and with rather ab- 

 ruptly attenuated ends ; its striae are 

 more difficult to resolve, and the texture 

 of its valves is thinner. 



P. laciistre (S.). — Lanceolate, consider- 

 ably flexed, gradually tapering into the 

 obtuse apices ; longitudinal and trans- 

 verse striaB, 48 in -001"; median line 

 subcentral. SD. i. p. 68, pi. 21. f. 217. 

 Fresh water. England. 1-144". 



P. TJiuringicum (K.). — Lanceolate, sig- 

 moid, gradually attenuated to the sub- 

 acute apices, obsoletely notched at the 

 middle of each margin ; median line 

 central; striae wanting or indistinct. = 

 Navicula Thuringica, KB. p. 102, pi. 4. 

 f. 27 ; Gyrosigma Thuringicum, Rab D. 

 p. 47, pi. 5. £ 4. Thuriugia. Front 

 view narrow-linear ; 1-264" to 1-168". 



P. Agellus (E.). — Large, lanceolate, 

 flexed, gradually tapering to the obtuse 

 apices, marked longitudinally with very 

 fine lines, and thus appearing furrowed ; 

 median line centra], = Nacicula Agelhis, 

 EB. 1840, p. 18; EM. pi. 15 a. f 31; 

 Gyrosigma Agellus, Rab 1). p. 47. Fresh 



water. Germany, Lough Mourne deposit, 

 Siberia. Front view nearly linear, vdih 

 subacute apices ; 180". Is more slender 

 and longer than P. Hippoccunpus, E. 



P. attenuatum (K., S.). — Large, elon- 

 gated, flexed, lanceolate, gradually at- 

 tenuated into the obtuse apices ; " lon- 

 gitudinal strife 30, and transverse 40 in 

 •001" ; median line central. SD. i. p. 68, 

 pi. "1% f. "nQ.^i Navicula attenuata, KB. 

 p. 102, pi. 4. £ 28 ; Gyrosigma attenuatum, 

 Rab D. p. 47. Fresh water. Em'ope. 

 1-120". Colour purplish broTvm; front 

 view narrow-lanceolate, with truncate 

 ends. 



P. cuspidatum (Rab.). — Slender-lan- 

 ceolate, very much flexed, with long, 

 tapering, obtuse ends ; median line cen- 

 tral. = Gyrosigma cuspidatum, Rab D. 

 p. 47, pi. 5. £ 5, 6. Fresh water. Europe, 

 America. It is always mixed with P. 

 acuminatum. 



P. acuminatum (K., S.). — Lanceolate, 

 tapering into the obtuse apices ; flexure 

 considerable ; median line central ; lon- 

 gitudinal striae 40 in -001", transverse 

 52 in -001". SD. i. p. 66, pi. 21. £ 209. 

 = Navicula acuminata, KB. p. 102, pi, 4. 

 £ 2Q ; Navicula Sigma, EB. 1843, p. 209 ; 

 Gyrosigma Hassallii, Rab D. p. 47. 

 Marine. Europe, Asia, Africa., America, 

 (ix. 146.) Front view narrow-linear, 

 with obtuse apices ; 1-162" ; colour 

 pale brown. 



P. Hippocampus (E., S.). — Large, 

 elongated, broadly lanceolate, obtuse ; 

 flexm-e considerable ; colour pale brown ; 

 striae as in P. attenuatum ; median line 

 central. SD. i. p. 68, pi. 22. £ 215. = 

 Navicula Hipjjocampus, E In£ pi. 13. £ 9 ; 

 Gyrosic/ma Hippocampus, HBA. pi. 102. 

 £ 11 ; Rab D. p. 47. Marine. Europe, 

 (ix. 145.) 1-166" ; front view linear, 

 truncate. 



P. Strigilis (S.). — Large, much elon- 

 gated, lanceolate, uniformly tapering to 

 the subacute apices, flexed ; median line 

 central ; striae, transverse and longitu- 

 dinal, 36 to 40 in -001". SD. i. p. 66, 

 pi. 22. £ 208. Brackish water. England. 

 Length 1-80"; breadth 1-830" ; colour 

 pale brown. Notable for its graceful 

 form and distinct striae. 



P. Seal]) rum (Gaillon). — Small, sig- 

 moid, gradually attenuated into the 

 rather obtuse apices, longitudinally 

 striated. = Cymhella Scalprum, AD. p. 11 ; 

 Navicula Scalijrum, E. In£ ; KB. pi. 4. 

 £ 25. Marine. Europe, xlsia, America. 

 Length 1-430" to 1-290". 



P. Normanii (n. sp.). — Broadly lan- 

 ceolate, slightly flexed, with rather ob- 



