918 



SYSTEMATIC HISTOEY OF THE LN^FUSOEIA. 



fine point ; transverse striae 48 in -001" ; 

 median line central. SD. i. p. 67, pi. 22. 

 f. 213. Brackish water. Essex. 



P. Apidum (Rab.). — Slender-lanceo- 

 late, niucli curved, with obtuse ends, 

 transversely striated ; front view broadly 

 linear. Rab D. p. 47, pi. 5. f. 7. Italy. 

 In the figiu-es the valves are linear, very 

 but not s}^llmetrically sigmoid, with 

 tapering- ends and central median line. 



2 1 Valves lanceolate, with oblique striae. 



P. delicatidmn (S.). — Slender-lance- 

 olate, gTaduaUy tapering to the acute 

 apices ; ilexm-e moderate ; median line 

 central ; striae oblique, 64 in -001". SD. 

 i. p. 64, pi. 21. f. 202. Brackish water. 

 Britain. Length 1-112"; breadth 

 1-1500". Colour pale pink. 



P. injiatum (Shadbolt). — Small, 

 broadly-lanceolate, with acute apices ; 

 median line central, much flexed, as well 

 as the' valve ; striae oblique. TM. ii. 

 p. 16, pi. 1. f. 9. Marine. Natal. 



P. decorum (S.). — Large, elongated, 

 rhomboid-lanceolate, imiformly flexed, 

 gradually tapering to the subacute apices ; 

 striae oblique, 36 in -001" ; median line 

 diagonal, marginal near the ends. SD. i. 

 p. 63, pi. 21.' f. 196. Brackish water. 

 England. Colour pale chestnut. 



P. amjidatum (Quekett, S.). — Large, 

 broad, sigmoid, rhomboid-lanceolate, 

 rapidly tapering to the subacute apices ; 

 median line somewhat diagonal ; stritie 

 oblique, 52 in -001". SD. i. p. 65, pi. 21. 

 f. 205. = Navicida angidata, Quekett, 

 Microsc. p. 438, pi. 8. f. 4 to 7. Marine. 

 Britain. Colour pale chestnut ) flexure 

 moderate. 



P. quadratum (S.). — Large, very 

 broad rhomboid, rapidly tapering to the 

 subacute apices, which are slightly flexed; 

 striae oblique, 45 in -001" ; median line 

 central. SD. i. p. 65, pi. 20. f. 204.= P. 

 amjidatum, ANH. 2nd series, ix. p. 7. 

 Marine. Em'ope. Colom' chestnut ; 

 lengthl-llO" ; breadth 1-428". Easily 

 recognized b3'its very broad angular form. 



P. Janceolatum (Donkin). — Straight, 

 broadly lanceolate, acute ; median line 

 straight or gently sigmoid, with the ter- 

 minal nodules tm'ned in contrary direc- 

 tions ; strife verv fine, oblique, about 70 

 in -001". TM. ;i. p. 22, pi. 3. f. 4. = P. 

 transversale, /3, Mr. Roper. Marine. Eng- 

 land. Straw-coloured ; -0055" to -006" : 

 front view narrow linear-lanceolate. 

 The extremely fine striae require the 

 most careful manipulation with very 

 obliqne light, to render them visible with 

 a superior l-5th objective. 



P. navictdaceum (Breb.). — Rather 

 small, lanceolate, straight, gradually 

 tapering to the obtuse apices, which are 

 slightly tm'ned in contrary directions ; 

 median line sigmoid, not central ; striae 

 very fine, oblique. B. Diat. of Cherbourg, 

 1854, p. 17, f. 7. = Gyrosigma transver- 

 sale, Microg. Diet. pi. 11. f. 37, 38 ;_ P. 

 transversale, SD. ii. p. 96. Marine. 

 Common, especially in deep waters. This 

 species, \dewed laterally, greatly resem- 

 bles a Navicida in its lanceolate straight 

 fonn. Its apices are only slightly in- 

 clined to opposite sides. The median 

 line, however, is sigmoid, and the striae 

 are oblique and decussating. 



P. marinum (Donkin). — Broadly lan- 

 ceolate, straight, slightly sigmoicl near 

 the obtuse ends ; median line sigmoid on 

 each side of the central nodule ; striae 

 oblique. TM. vi. p. 22, pi. 3. f. .3. Marine. 

 Northumberland. Straw-coloured ; striae 

 about 45 to 50 in -001". _ -0055" to -006". 

 The well-marked sigmoid flexm'e of the 

 median line on both sides of the central 

 nodule distinguishes this species, and 

 renders it easy of recognition. 



P. Nuhecula (S.). — Small, lanceolate, 

 nearly straight, with obtuse apices, cen- 

 tral median line, and 55 oblique striae in 

 •001" ; colour veiy pale. SD. i. p. 64, 

 pi. 21. f. 201. Marine. England. 



P. intermedium (S.). — Elongated, pale 

 sti'aw-colom', slender lanceolate, nearly 

 straight, tapering to the subacute apices ; 

 median line subcentral; striae oblique, 

 55 in -001". SD. i. p. 64, pi. 21. f. 200. 

 Marine. England. 



V. rigidum {^.). — Large, stout, pale 

 straw-colour, lanceolate, nearly straight, 

 with rounded apices ; median line cen- 

 tral; striae oblique, 48 in -001". SD. 

 i. p. 64, pi. 20. f. 198. Marine. England. 



P. validiim (Sh.). — Large ; lanceolate, 

 nearly straight, with very obtuse apices, 

 oblique striae, and slightlv flexed median 

 line. MT. ii. p. 16, pi. 1. f. 8. Marine. 

 Natal. 



P. elongatum (S.). — Large, much 

 elongated, lanceolate, gradually tapering 

 to the acute apices, nearly straight, ex- 

 cept at the ends, which are slightly 

 curved ; striae oblique, 48 in -001" ; 

 median line nearly straight. SD. i. p. 64, 

 pi. 20. f. 199. Marine. England. Clear 

 straw-colour. Length 1-75"; breadth 

 1-920". 



P. strigosum (S.). — Large, elongated, 

 broadly lanceolate, gradually attenuated 

 to the obtuse apices ; flexure slight ; me- 

 dian line not central near the ends ; 

 ^% oblique, 44 in -001". SD. i. p. 64, 



