20 JOHNSTON, ON DIATOMACKiE. 



months previously, and had distributed it under the MS. name 

 of ScapJia clathrata. Mr. Edwards at once recognised from 

 my description the identity of his Scapha with my Gephyria, 

 and it is in consequence of his strong remonstrance against 

 the union also of Entopyla that I have now revised the whole 

 subject, and have stated my opinion as above. 



In the Elide guano form, it is doubtful whether Mr. 

 Johnston speaks of the dots or of the costse, when he says 

 there are 26 in '001 ; probably of the former, for, according 

 to my measurement, there are only 11 costa3 in *001 in all 

 my specimens. So that in this respect it is intermediate 

 between G. incurvata and G. Telfairice. In general appear- 

 ance it resembles the latter more than the former, but 

 the valves are much more obtuse than in any specimen of 

 the species from Mauritius. How far these are sufficient 

 marks of distinction I have not materials to decide. If 

 these two be admitted as different, the one I indicated 

 ('Micr. Journ./ vol. vi, p. 164-) from the west coast of 

 Australia may prove a fourth ; and I have observed valves of 

 the same genus from other places, but about which I can 

 offer no opinion without seeing perfect frustules. On some 

 future occasion I may have it in my power to elucidate all 

 the species more than I can do at present. 



Gephyria, Arnott (nov. gen.) 



Frustules arcuate, attached (not? forming a continuous fila- 

 ment), destitute of cellulate annuli and septa ; connecting zone 

 sub-lamellate, finely striate on the surface. Valves arcuate, 

 with one median and several lateral costse, dissimilar : 

 inferior with the costse disappearing below the extremities of 

 the valve ; superior with them reaching the extremity. 



1. G. incurvata. — Costae on the valve about 7 in *001. 

 Eupleuria incurvata, Arnott ; Acnanthcs costatus, Johnston. 



Hah. Ichaboc (in guano) ; St. Simon's Bay, South Africa ; 

 Patagonia (in guano). 



2. G. media. — Valves obtuse; costse 11 in -001. Scapha 

 clathrata, Edwards, MS. ; Achnanthes angustata, Johnston 

 (not of Grcvillo). 



Hah. Elide Island, California (in guano). 



In Botany clathrate implies that there are openings 

 between the costso, so cannot with justice be applied to this 

 species. 



8. G. TelfamtB. — Valves cuncate, and acute at the ex- 

 tremities ; costae 15 in "001. 



Hub. Mauritius. 



