388 DESCBiPTiON OF [Foli/f/astrica. 



nated. It is large, striated, rather curved ; ends widely rounded. 

 (P. 24, f. 16 and 17.) Xorth America. 



HiMANTiuiUii FajJilio. — Striated laterally, much expanded at the 

 centre ; subijuadrate, furrowed dorsally, and bidendate ; constricted 

 near the obtuse apices. (P. 15, f. 45, 49, 50, 51, and 52.) 



H. jxirallelum. — Linear, finely striated, curved ; dorsal convexity 

 and ventral concavity uniform, lines parellel ; apices simply rounded. 

 Ehrenberg has seen six wands united. Small specimens resemble 

 Eunotia Faba. Length 1 -240th. British guano. 



H. Arms == Eunotia Arcus. — Striated, convex on the dorsum ; 

 plane on the venter, constricted ; ends roimded, rather recurved ; 

 Btri«B eleven in l-1200th. Length l-480th to l-280th. By its 

 imperfect fission it forms chains, as in Fragilaria. Fossil in 

 Sweden, and living at New York, Berlin. 



H. pectinale, (Kiitz) = Fragilaria pectinalis (Ealfs.) — Large, very 

 finely striated ; apices on secondary side, rather incurved and rounded ; 

 the dorsum slightly expanded, plane ; venter somewhat hollow. 

 Length of frustule l-300th. 



H. minus. — Small, quite smooth; conjoined frustules forming 

 elongated filaments, the dorsum and venter constituting the free or 

 exposed surfaces. On fresh-water Algse. Length l-900th. 



H. Suhirolii. — Of moderate size, very smooth; on primary side 

 oblong-elliptic, or semi-elliptic ; on secondaiy side, linear, lunate, with 

 rounded apices. Length l-384th. (P. 17, f. 13.) 



H. Veneris. — Of middling size, quite smooth, plane on one side, 

 convex on the other, with acute extremities. Tiinidad. 



Genus Hyaxodiscus. — Lorica composed of two equal orbicular 

 valves, not in chains ; discs not perforated ; destitute of septa ; the 

 centre of the disc separable (soliibiLis), valves equal, disciform, with a 

 smooth siu'faee. In form, it resembles Craspedodiscus. 



H. lavis. — Smooth, both at the centre and margin, large, discoid- 

 Allied to Biscoplea phifsoplea. Diameter 1 -456th. Vii'ginia. 



H. (?) Fatagonicus. — Large, very smooth, flattened; suture of the 

 valves remai'kably tumid ; margin of disc sej)arable ; its suture 

 slightly sulcate, not denticulate. Diameter 1 -432nd. In pumice, 

 fi'om Patagonia. 



