33-1 DESCRIPTION OF {I*oly(jastru-a. 



CoccoifEis prceiexta. — Small, elliptic, -with six longitudinal lines 

 on each side of the centre ; and a dilated, smooth, areolar margin. 



C. punctata. — Veiy small, elliptic, with eight longitudinal lines 

 each side of the median line. Mexico. 



C. (?) Crux. — Smooth, elHptic, slender, with a transverse linear 

 umbilicus. Diameter l-1632nd Bermuda., 



C. rhomhea. — Of the form of a rhombus, with generally thi'ee 

 longitudinal lines each side the centre. Length l-1200th. Alive 

 at Niagara. It is very like C. Mexicana and C. Americana. 



C. AmpMceros — Eoughly striated ; navicular on the side ; each 

 extremity suddenly attenuate and much prolonged (rostrate), 

 narrowly linear on the back. Length 1-5 76th. Marine at the 

 mouth of the Elbe. See Rhaplioneis Amjylnceros. 



C. //;«5«^«.— -Sub-orbicular, elliptic, with a porous wide margin ? 

 disc with twelve longitudinal fine lines passing along its middle ; 

 ends widely roimded. Length l-576th. Salzberg. 



C. (?) Navicida — Striated ; navicular on the sides ; narrowly 

 linear on the back, with an indistinct central longitudinal J"sulcus 

 (furrow.) Length l-864th. Marine. The Elbe; parasitic on 

 Bacillaria paradoxa. 



C. Rliombus = Ehaplioneis Ull^^his. 



C. (?) margaritlfera. — Broadly ovate ; each end subacute, with 

 transverse granular striae, like rows of pearls. It is closely allied to 

 C. Mexicana, but rather larger and not curved. Bosphorus. 



C. scutum. — Found by Ehrenberg, in. earth from jSTew Holland. 



C. disciformis. — From the same locality. 



C. no/vicularis. — From the same locality. 



C. gemynata. — Found in the chalk marl of ^gina. 



C. occanica (Ehi'.) — Ellij)tic, suborbicular, convex, marked by 

 simple curved and concentric lines ; not undulated ; transverse striae 

 none. Length l-1150th. In sea water, Callao, Peru. (P. 15. f. 

 42.) Kiitzing describes this species as roimded, with numerous 

 very delicately punctate longitudinal lines. Length 1 -624th. Baltic, 

 North Sea, Peru, &c. He considers it identical with Ehrenberg's 

 species ; but it has curved and concenti'ic lines. 



C. pt/ffinwa (Kiitz.) — Minute, elliptic, very smooth, sun'ounded by 



