ZOOLOGICAL AND BOTANICAL ASSOCIATION. 85 



Hud it not been for its close resemblance to C. aurita (Busk), evi- 

 dently a true Catenicella, and with which it often grows associated, one 

 might have almost been inclined to consider this curious little form 

 the type of a new generic group, or an aberrant species of the genus 

 Calpidium. As in Calpidium, the cells have two "key-holes;" but a 

 single glance must satisfy us that the cell consists of a primary and a 

 secondary chamber, bearing the same relation to one another that the 

 two cells of a geminate cell bear at a bifurcation in any of the other spe- 

 cies of the genus. C. geminata bifurcates at every cell, so that all the 

 axial cells are geminate. The septum between the cells is traced on the 

 back of the cell by a deep groove in the usual position. The back of the 

 primary cell, both in this species and in C. aurita, is frequently perfo- 

 rated to give origin to a horny, tubular tendril. The secondary cell 

 sometimes gives off a secondary axis, but more usually only a single 

 wedge-shaped cell, apparently partially abortive. The ccenoecium is 

 very calcareous, and becomes very thick with age, a calcareous deposit 

 •obliterating all the markings. The horny connecting tubes between the 

 cells are unusually long. 



2. — CoTHUBNICELLA, W. g. 



Cells in simple rows, each row arising from the side of a joint of an 

 articulated stem, each cell springing from the upper and back part of 

 another by a short horny tube. Cells all facing the same way. 



Cell-mouth provided with a movable operculum. Ovicell an ordi- 

 nary cell of a series, much enlarged, but scarcely modified in form. 



C. dadala, n.s. Plate VIII., Figs. 3, 4, and 5. 



The only known species. 



This genus seems to have a sufficient number of characters in com- 

 mon with Catenicella to warrant its admission into the same family. It 

 is, however, at once distinguished from the rest of the Catenicellidao by 

 its simple rows of cells arising regularly from the joints of an arti- 

 culated stem. The joints of this stem appear to be abortive cells. 

 The last joint of one branch is often dilated into a cell, while the 

 other branch ends in a single or double tendril of narrow joints, and the 

 final cell of a row is frequently capped by a similar tendril, representing 

 a continuation of the series. In C. dadala the stem is at first simple, 

 then makes a single bifurcation, and the cells start in straight rows, a 



