4 Dr. R. K. Greville on new Genera and 



Genus Asterionella. 



Asterionella Synedraformis, n. sp., Grev. PI. V. figs. 5, 6. 

 Frustules exactly linear throughout^ truncate, with two minute 



apiculi at the apex ; valve slightly dilated and rounded at the 



base. 

 Hah. Hongkong Harbour; J. L. Palmer, Esq. 



A very fine and distinct species, agreeing only with A. Ralfsii 

 in the frustules being exactly linear ; but the latter is a fresh- 

 water species, having, besides, the valve of a diflferent shape. 

 The present species is a large one, the frustules being sometimes 

 •0080" and upwards in length. Towards the apex the margins 

 appear to be thickened, and terminate in two minute apiculi. 

 The valve is transversely striated, shortly acuminated at the 

 apex, becoming more slender below (as in other species), and 

 then slightly dilated at the base. The late Prof. Smith com- 

 mitted an oversight in resting the character of the genus partly 

 upon the frustules being " inflated towards one or both extremi- 

 ties ;" for he defines one of his own three species {A. Ralfsii) as 

 " on F. V. exactly linear," which they are. This is of little 

 consequence, as the main character depends upon the stellate 

 arrangement of the frustules, combined with the form of the 

 valve, which is different at the two extremities. Our new spe- 

 cies appears to be abundant at Hongkong. I have one specimen 

 in my cabinet in which only two frustules are absent from a 

 circle of fourteen. 



Genus Surirella. 



Surirella Palmeriana, n. sp., Grev. PI. V. fig. 7. 

 Valve ovate-oblong, with obtuse ends ; alse inconspicuous ; costse 

 very slender, numerous, regular, terminating in a narrow me- 

 dian line, and having very delicate intermediate striae. 

 Hab. Hongkong Harbour ; in material communicated by J. L. 

 Palmer, Esq. 



A very fine species, allied to S. gemma, but differing in im- 

 portant particulars, especially in the total absence of alae, and in 

 the canaliculi being equally distant. It is, besides, a much 

 larger species. Prof. Smith gives the length of S. gemma at 

 from -0025" to -0058"; that of S. Palmeriana is -0080". The 

 canahculi are 4 in -001", and the intervening spaces are beauti- 

 fully arched or crenate at the margin. It appears to be exceed- 

 ingly rare, as Mr. Palmer has not referred to it in his letters. 



Genus Creswellia. 



Creswellia annulata, n. sp., Grev. PI. V. fig. 8. 



Minute ; frustules short, cylindrical, truncate, transversely stri- 



