Naviculacea.] infusorial animalcules. 389 



In Hyalodiscus Iccvh, the suture of tlu> valves is not tumid ; and not 

 the margin oiilj^ but the central part also, of the discs, sepai-able 

 (solubilis). Do these two species, therefore, rightly fall together in 

 the same genus ? 



Genus Lipaeogtea, (Ehr.)— Cylindrical, utricular, tnineate. Each 

 utricle spontaneously divisible transversely through its middle ; 

 closed at the extremities, "snth an internal wall, and a spiral filiform 

 crest. No aperture evident, but muiute ones may probably be present 

 on the denticulated margin ; no internal septa. If occurring 

 in chains ? 



This genus, if the individuals be isolated, approaches Pyxidicida ; 

 but if they are concatenated, which is doubtful, it becomes allied to 

 GalUonella. Inhabit, it approaches very closely to the non- siliceous 

 genus of plants, Sjnrogyra. 



L. dendroclioira. — Smooth, ciystaUine, margin of discs denticulated, 

 with an internal spiral band; thirteen turns in. 1 -360th. Figure 

 utricular, the length exceeding the breadth three to four times. 

 Length l-360th. Breadth 1-1 728th. Found on the roots of water 

 plants. Its internal contents are green when diied. 



L. cirmlaris. — Smooth, crystalline, margins denticulated, with 

 internal annular filaments; tliirteen turns in l-360th. Length l-360th. 



Ehrenherg says, he has not yet determined, satisfactorily, whether 

 the preceding are distinct species, or merely varieties of one species. 

 Each has a smooth disc, with three central apicuH. 



Genus Mastogonia, (Ehr.) — Lorica (unequally) bivalve, not in 

 chains ; valves with protuberant angles, orbicular at the base ; um- 

 bilicus unarmed. 



Some forms of this genus were originally placed among the 

 Pyxidicula, but clearly diifer by theii' unequal and angular valves, vnth 

 radiating veins, and non-ceUular siu'face. They differ, to a like 

 extent, also from Actinoct/clus. 



M. crux. — Large, one valve ^dth four crucial angles and rays, the 

 other with seven, apices not truncate. Diameter 1 -396th. Bermuda. 



M. qicinaria. — One valve "oath five angles and rays ; apex not trun- 

 cate. Diameter 1 -480th. Bermuda. 



Mastogonia Eota. — One valve with six angles and rays; the 

 other with seven, apices entire. Diameter 1- 360th. Bermuda. 



