OP TKE NAYICTJLE.i:. 



921 



cnstata, EB. 1854, p. 240 ; EM. pi. 35 

 BB. 4. f. 13. Atlantic. 



D. inversa (E.). — Short, narrow, sig- 

 moid, with subacute apices ; front view 

 very broad, quadrangular, constricted at 

 the middle, with broadly truncate ends 

 and marginal glands. = iVflric«</a inversa, 

 EB. 1840, p. 18. Europe. 1-576". " It 

 is allied to Amphiprora alata, but wants 

 the winged portions" (E.). 



D. carinata (Donkin). — Straight, linear- 

 lanceolate, acute, very convex ; colour 

 dull pui-ple; median line strongly sig- 

 moid, marginal near each end j striae 

 oblique, fine, about 55 to 60 in -001". = 

 Pleurusigma carinatum, Donkin, I. c. p. 23, 

 pi. 3. f. 5. England. -0046"; valve 

 twisted ; median line diagonal at the cen- 

 tre, marginal near the ends. (\T:n. 49.) 



I), compact a (Grev.). — Straight, very 

 convex, linear, obtuse, sigmoid from 

 having the ends sloped in contrary 

 directions ; median line much flexed, 

 diagonal at the centre, marginal near 

 the ends ; striae very fine, 53 to 60 

 in '001". =Pleurosig ma cotnpactum, MJ. 

 V. p. 12, pi. 3. f. 9 J Pleurosigtna rectum, 

 Donkin, TM. vi. p. 23, pi. 3. f. 6 ; Am- 

 phiprora Ralfsii, Amott, MJ. vi. p. 91. 

 Britain. -0045" to -005". According to 

 Dr. Donkin, the striae are longitudinal 

 and transverse ; colour very pale. 



D. minuta (Donkin). — Short, very 



convex, linear-oblong, subacute, sigmoid 

 from the sloping of one margin near each 

 end in contrary directions ; median line 

 much flexed ; striae very fine, transverse 

 ones distinct, about 55 in -001", longi- 

 tudinal ones obscure. =Pleu7'osipna mi- 

 nutum, Donkin, /. c. p. 24, pi. 3. f. 8. 

 England. -0025" ; colour, very pale 

 brown. D. minuta seems to differ from 

 D. compacta, to which Professor Arnott 

 would unite it, chiefly in its smaller size. 



D. angusta (Donkin). — Very con- 

 vex, linear, with acute, slightly apicu- 

 lated apices ; median line strongly sig- 

 moid, marginal, except a central diagonal 

 portion -, striae obscure, longitudinal. = 

 Pleurosigma anqustum, Donkin, I. c. p. 24, 

 pL 3. f. 9. England. -005" to -0055"; 

 colour dull piu'ple. Another form closely 

 allied to D. compacta. 



D. reticulata (Norman, 3//S'.). — Linear- 

 lanceolate, with rather obtuse apices ; 

 median line strongly diagonal at the 

 centre, then marginal and slightly pro- 

 jecting; striae oblique, distinct, 22 in 

 •001". Stomach of Ascidians, Shark's 

 Bay, Australia. Collected by Dr. Mac- 

 donald. Colour pm-plish brown; front 

 view oblong, with truncate ends and con- 

 stricted middle. For the description of 

 this species we are indebted to George 

 Norman, Esq. 



Genus AMPHIPROEA (Ehr.) (Entomoneis, Elir.). — Frustules free, simple, 

 in front view constricted at the middle ; valves convex, with a longitudinal 

 wing, and central and terminal nodules ; striae, when present, transverse. 

 Marine. Amphiprora is distiQguished by its lateral wings, which are con- 

 stricted at the middle, so that the frustule in front view, when not twisted 

 (which, however, frequently occurs), is more or less panduriform, with trun- 

 cate or broadly -rounded ends. The late Professor Smith stated that the 

 peculiar frustules of this genus could not be confounded with any others, 

 save those of a few species of Nitzschia. Erom the recent discoveries of 

 Dr. Donkin, Amphiprora is found far more closely allied to Pleurosigma 

 and Donkinia. Erom these genera it diff'ers by its alate valves, and by 

 having transverse striae only. According, ho\v^ever, to the late Professor 

 Gregory and Dr. Donkin, the valves of Amphiprora are furnished, in addition 

 to the median crest, with lateral ones also, similar to those of SurireUa ; and 

 certainly the frustules in the front view most frequently exhibit a longitu- 

 dinal line on each side between the margin and the central portion — an 

 appearance not unlikely to depend on such a formation, particularly in A. 

 ornatci and A. p)aludosa, in which these lines are undulated. An end view 

 is required to ascertain whether this be really the case, since the same 

 appearance would result from a depression along the sides of the median 

 crest, and even the undulations may be produced by transverse ridges. 



Amphiprora alata(E.,'K.'). — Very hya- 

 line, generally twisted ; front viev/ broad- 

 ly winged, strongly constricted ; wing con- 



tinued round the ends ; lateral \-iew with 

 apiculate ends and a double line of puncta 

 accompanjdng the keel; striae 42 in 



