NEW SPECIES OF DIATOMACEAE. 9 



Southern and Antarctic Oceans. Other species are common in Guano, and others 

 occur as fossils in the "Bermuda Tripoli," and in the infusorial strata at Richmond, 

 Virginia. The species liere described was found in considerable numbers with 

 other Diatomaceae in the contents of the stomach of the Bulrijodacti/la (jrandis, 

 Ayres, a large Holothuridian animal from St. George's Bank, for specimens of which 

 I am indebted to William 0. Ayres, Esq., of Boston. 



It is the first of the genus which has been found as a living species in the north- 

 ern hemisphere. Its southern congeners abound in a frozen ocean. 



Chaetoceros incurvuin, B. 



{rLATE, Figs. 30?, 31, 32.) 



Bases elliptical ; horns i-ecurvcd, longer than the body. Frustules usually found 

 united in pairs, with a void space between them. Sometimes a fillet with the 

 curved horns is found unconnected with the other portions (see Fig. 31). 



I have only noticed this curious form in the infusorial strata at Richmond, Vir- 

 ginia, where it is not rare. 



Denticula? laiita, B. 



(Plate, Figs. 1, 2.) 



Bases elongated, oblong or elliptical, with three to sixteen distant transverse 

 striae, or bars, which pass on to the sides, where they terminate in an ocellate form. 

 Sides rectangular, showing near each margin a row of the ocellate ends of the basal 

 striae or bars. Length, 2'"; width, i"*. 



This species forms a large portion of the mass of fossil Diatomaceae at Suisun 

 Bay, California. 



Gallionella crotonensis, B. 



(Not figured.) 



Frustules minute, about twice longer than broad, united by pairs into long fila- 

 ments, and showing two sulci or lines of division between the ends of each pair. 

 Internal portions not constricted. Surface with decussating rows of very minute 

 granules. Bases of the frustules slightly crenulate. Average length of joints, 

 J". Diameter, -i-"". to i"". 



I should be very reluctant to add another species to this already confused and 

 imperfectly known genus, if I could satisfactorily refer our species to any of the 

 described forms. But it is only by overlooking characters which are obvious enough 

 under good glasses, that I can make it appear to agree with any of the published 

 descriptions. 



It might at first be confounded with either O. decussaia, G. creniduta, or with the 

 young of O. auriclmlcea, Ehr. ; but, although decussately punctate, it differs from 

 Q. decussa(a in the extreme delicacy of its granulations ; although crenulate, it is 

 far less distinctly so than O. cremdata, and from O. aurichalcea, for the young of 

 which it is usually mistaken ; it differs in the small and nearly uniform size, its 

 want of internal constrictions, and in its surface appearing distinctly decussately- 

 punctate under a power which shows scarcely a trace of granulations on the surface 

 of Q, aurichalcea. 

 2 



