EEPOET O.N THE DIATOMACE^E. 137 



London, new series, vol. ix. p. GO, and defined it in the following manner : — " Frustules 

 free, disciform ; disc with radiate or scattered cellules or puncta in the middle portion, and 

 a circle of large intramarginal cellules." The genus has hitherto comprised only the two 

 species Hctcrodictyon rylandsianum, Grev., and Ileterodictyon splendidum, Grev., both of 

 which were found by Greville ' in the Barbados deposit, Cambridge, U.S.A. ; but I am of 

 opinion that the former, on account of the corona of large linear or oblong cellules with 

 which it is provided, should be ascribed to the genus Asterolampra, and named Astero- 

 lampra vulgaris, Grev., 2 which is from the very same deposit, and of which other six 

 different forms have been given. 



Heterodictyon jerrreysianum, n. sp. (Plate XXI. fig. 8.) 



Disciforme ; medio inordinate cellulosum ; subtriangularium areolarum corona submar- 

 ginali ; spatiis intramarginalibus cellulis decrescentibus obsitis. Ad insulas Phdippinas. 



This new species was collected in the neighbourhood of the Philippine Islands. Though 

 its elegant form might at first sight be mistaken for that of Asterolampra marginata, 

 Grev., 3 it may be readily distinguished from the latter, in which the central part is covered 

 with puncta disposed in radiating lines, by having the sculpturing arranged without order. 

 The corona of large cellules on the submarginal area is composed of subtriangular 

 compartments, two of the angles being blunted at the points of contact with adjoining- 

 compartments. The cellules in the intramarginal segments, circumscribed by the sub- 

 marginal belt, diminish towards the periphery. 



The specific name has been given in honour of the well-known English naturalist, Dr 

 Gwyn Jeffreys. 



Brightwellia, Pialfs. 



This genus was established by Ralfs in honour of the well-known microscopist, 

 Brightwell. The Diatom, which the latter observer had named Craspedodiscus coronatus, 4 

 was found to differ from the other members of that genus by the possession of a corona of 

 oblong cellules, which separated the central from the peripheral part of the disc, and Ralfs/' 

 who first drew attention to this important circumstance, ascribed the frustule to his new 



1 Micr. Journ., n. s., vol. iii. p. 66, pi. iv. figs. 6 and 7. 



2 Micr. Journ., n. s., vol. ii. p. 47, pi. vii. figs. 17-22. 



3 Micr. Journ., n. s., vol. ii. p. 50, pi. viii. fig. 30. 



4 Brightwell on some of the Earer or Undescribed Species of Diatomaceae, Micr. Journ., vol. viii. p. 95, 

 pi. v. fig. 6. 



'•> Pritchard, op. cit., p. 940. " This species is very variable in size. In a dry state it is of a purplish or 

 brown colour, but in balsam hyaline ; the centre has the granules irregular near the umbilicus, and interrupted 

 by blank rays ; but near the circlet of cellules they become more regular, and form curved, moniliform lines. 

 The broad limb is usually brownish when dry, and marked by numerous radiating lines similar to those of 

 Coscinodiscus concinnus, and have in the intervals extremely minute obliquely arranged granules. The radiating 

 lines, although conspicuous in the dry state, nearly disappear in balsam." 



(bot. chall. exp. — part iv. — 1886.) -D 18 



