249 



Calpidium Busk, char, emend. 



The sternal area has 5 fenestrse disposed in a curve and an inner cryptocyst 

 lamina. The aperture, the anter of which is surrounded hy a strongly projecting 

 margin, has a trilobed or triangular sinus ending in a point, and is provided 

 with two very strong hinge-teeth, projecting within the aperture. The rosette 

 plates of the lateral chambers are placed in small rounded depressions and 

 may therefore be looked upon as multiporous. The occlusion takes place in a 

 way similar to that in Scuticella. 



In the two species of this genus the lateral chambers occupy much more 

 than one half of the surface of the single zooecia as well as of the bi- and tri- 

 zooecial internodes. They occupy especially the greater part of the distal as well 

 as of the basal surface, being separated here only by a number of elevated ridges, 

 each furnished with a longitudinal furrow. 



Calpidium ponderosum Goldstein. 



Catenicella ponderosa Goldst., Journal Micr. Soc. Victoria, 1880, pag. 63. 



(PI. XXI, figs. 5 a— 5 e. Pi. XIII, figs. 1 a-1 d). 



The zooecia are oval and the sternal area, which is longer by at least a half 

 than the aperture, is provided with five large, pear-shaped fenestra separated by 

 narrow ribs, in the marginal portions of which a generally strongly developed 

 cryptocyst appears. Inside the sternal area is a large, obliquely oval cryptocyst 

 lamina. The aperture is oblong and separated by a constriction into an anter, 

 the two lateral margins of which converge towards the constriction, and a tri- 

 angularly trilobed poster. The sternal sinus is mainly preserved in the form of 

 the small, triangular sinus of the aperture, but immediately on the proximal side 

 of it an extremely short sutural line is seen, in which two very slightly devel- 

 oped and somewhat protruding ribs meet. Within each of the two processes 

 bounding the constriction we see a robust, cylindrically conical hinge-tooth, which 

 however does not project freely into the aperture itself, when the latter is seen 

 from the frontal surface. The anter of the apertui-e is surrounded by a large, 

 obliquely protruding, bilobed, umbellate expansion, the two triangularly rounded 

 lateral halves of which are separated by a broad, but low, obtuse-angled 

 incision. 



The lateral chambers. The scapular chamber is not everywhere developed 

 as an avicularium, and the latter is not infrequently wanting on one side in the 

 single zooecia as well as in the bi-zooecial internodes. The three other lateral 

 chambers have a membranous roof and occupy a very large part of the surface 



