OF THE MELOSIRE^. 



813 



C. stylorum (Br.). — Valve with styli- 

 fomi rays diverging from the centre, and 

 ending near the margin with a large 

 circidar head; centre irregularly punc- 

 tate. Sierra Leone. Br TMS. viii. p. 96, 

 pi. 6. f. 16. 



C. ? radiata (Br.). — Valve with simple, 

 strongly marked radii, reaching nearly to 

 the centre ; centre smooth ; in front view 

 the ends of the radii appear as pimcta. 

 West Indies, Monterey. Br. /. c. p. 96, 

 pi. 6. f. 11. As many as ten frustiiles 



have been found in union; this may, 

 therefore, belong to Melosira. 



C. punctata (S.). — Frustules with un- 

 dulations ; valves delicately punctate or 

 cellulate ; cellules radiate. Diam. -0008" 

 to -0015". Fresh water. England. SBD. 

 ii. p. 87. (^^II. 13.) 



C. Dallasiana (S.). — Valves with mar- 

 ginal costse ; centre cellulate ; cellules 

 irregular. Length of costae 'OOOS"; Diam. 

 of valve *022". Brackish water. Eng- 

 land. SBD. ii. p. 87. 



Genus ACTI^N'OGONIUM (Ehr.).— Frustules suborbicular, many- angled ; 

 disc smooth, mth radiating lines. Actinogonium, like Liostephania, differs 

 from the rest in being; smooth. 



Actinogonium septenarium, EM. pi. 

 36. I 39. Barbadoes. Rays (7) divid- 

 ing the disc into compartments, separated 

 from the margin by a regularly-undu- 



lated border. Between the centre and 

 border is a circlet of very short lines, two 

 in each compartment, (v. 55.) 



Genus LIOSTEPHANIA (Ehr.). — Frustules simple, orbicular; disc smooth, 

 but with a crown of rays encircling a large smooth central space or umbi- 

 licus. Liostephania is distinguished by its disc being smooth, and having a 

 circlet of striae, which striae do not reach the margin. 



Liostephania Rotula (E.). — Disc 

 having from six to foiu-teen simple rays. 

 EM. pi. 36. f 40. Barbadoes. (v. 57.) 



L. comta (E.). — Disc with from six to 

 thirteen rays, connected exteriorly by a 

 circlet of puucta. EM. pi. 36. f 41. 

 Barbadoes. This species differs from 



the preceding one in the presence of 

 puncta. 



L. magnifica (E.). — Disc -wdth its rays 

 alternating inwards with pairs of very 

 short striae, and connected exteriorly by 

 a circlet of puncta. EM. pi. 36. f. 42. 

 Barbadoes. (v. 56.) 



Genus DICTYOLAMPE-A (Ehr.). — Frustules orbicular, not concatenate ; 

 disc without an umbilicus, but having a circular cellular centre, with radiat- 

 ing striae, which alternate with other striae from the margin. 



Dictyolampra differs from the other genera of this family by its disc being 

 cellulose only in the centre, and indeed it probably ought, together with Lio- 

 stephania and Actinogonium, to form a distinct family ; but, having seen 

 no specimens, we are unable to decide on their proper position. 



Dictyolampra ^ella (EM. pi. 36. f 



38). Barbadoes. The only species. In 

 the centre is a large, circular, loosely cel- 

 lulose imibilicus, with numerous (about 



20) short radiating lines, which alternate 

 with similar ones directed inwards from 

 the margin ; between the latter are inter- 

 posed very short marginal striae, (v. 58.) 



Genus MASTOGONIA (Ehr.).— Frustules simple (unequally), bivalved; 

 valves not cellulose, in lateral view circular, unarmed, with lines radiating 

 from a stellate or angular umbilicus. These forms, which were formerly 

 placed in Pyxidicula, may be recognized by their unequal and angular valves, 

 radiating veins, and noncellular surface. The definitions of the species in this 



geniLS are unsatisfactoiy, depending almost entu-ely on the number of rays 



a character which we regard as very variable. 



Mastogonia Crux (E.). — Valves pl.33. 18. £8. Bermuda. Diam. 1-396". 

 large, one with fom-, the other with seven Umbilicus stellate, 

 radiating lines : apex not truncated. EM. M. quinana (E.). — Valves laro-e one 



