KEPORT ON THE DTATOMACE^E. 61 



well as its marginal alae are striated, while each of the area3 between the canaliculi is 

 ornamented by a grannie or ocellus. 



Surirella multicostata, n. sp. (Plate X. fig. 6.) 



Forma cuneata ; area centrali hyalina lanceolato-cuneata, et lineolarum corona 

 terminata ; numerosis costulis vel canaliculis (58) radiantibus ; margine et spatiis inter- 

 stitial ibus striatis. Ad Zebu. 



This large cuneate valve, which was collected in the neighbourhood of Zebu, is 

 provided with a smooth central lanceolato-cuneate area, which is circumscribed by 

 irregular rows of small transversely disposed lines. It is distinguished by the possession 

 of a corona of very numerous canaliculi or radiating costules. The marginal alae, the 

 interspaces between the canaliculi and the border, are delicately striated. 



Surirella thaitiana, n. sp. (Plate XIX. fig. 3.) 



Valva obovata, area lanceolata centrali transverse undulata, et lineolis terminata, 

 canaliculis duplici ordine radiantibus ad verticem striatis ; margine evidenter granulate 

 In portu Thaiti. 



This elegant frustule was found in a rich collection made at a small depth at the port 

 of Tahiti. It possesses an oval profile, and is provided with a central lanceolate area, 

 which is circumscribed by a row of small lines, and also presents a few slight undulations. 

 Its double row of medially constricted canaliculi are not separated by any interspaces, 

 and the canaliculi exhibit at their extreme ends an incipient serrated striation. The 

 margin is evidently granulated, and at its narrow extremity there are to be found a few 

 canaliculi, which are hardly outlined, and which indicate the locality in which the increase 

 of the Diatom occurs — a process which generally is bilateral and takes place at the poles 

 of the valve. 



Surirella grandiuscula, n. sp. (Plate X. fig. 5.) 



Forma subovata, e majoribus; area hyalina centrali lineolarum ordine interrupto cincta; 

 canaliculis inaequalibus per alas intercedentes et in alas marginales exeuntes distinctis ; 

 margine et alis striatis. In mari Pacifico. 



This Diatom, which is of unusual size, was obtained in a sounding of great depth 

 made in the centre of the Pacific Ocean. Its long axis measures not less than 196 M-, and it 

 possesses a slightly ovate form with a large smooth central area,, which is circumscribed by 

 an interrupted irregular row of short lines. There is a circlet of large canaliculi, which 

 become a little shorter and narrower as they approach the inferior or narrow extremity, and 

 are separated by interspaces which terminate in marginal alae. These alas and the large 

 border are striated, while, at the same time, a small group of striae mark the centre of 

 each intercanalicular space. 



