238 



is also developed as an avicularium on the adzocecial side of the daughter-zooe- 

 cium, is very small, arched and rather strongly projecting. The adzocecial, infra- 

 scapular chamber of the mother-zooecium is not developed. 



The oceciutn. The gonozooecium springs from a mother-zooecium and is of 

 about the length of an ordinary zocEcium, but much broader and 3—4 times as 

 long as the small, cap-shaped, covering kenozooecium. The structure of the sternal 

 area is similar to that of the ordinary zooecia, and this may also be said of the 

 lateral chambers on the adzocecial side with exception of the first one, which is 

 smaller and more steeply ascending. On the adzocecial side of the gonozooecium 

 the lateral chambers are much more faintly developed, situated almost vertically 

 on the frontal wall, and the scapular chamber is not developed as an avicu- 

 larium. No unpaired, median pores are found, and within the two transversely 

 oval fenestrse, which are here quite frontal, we find but one group of spinous 

 processes and no pores. On the top of the kenozooecium there is a rather large, 

 quadrangular or triangular chamber, compressed from front to base, which is 

 sometimes undivided, sometimes divided by two septa into three cavities, of which 

 the central one was not developed as an avicularium on any specimen I have 

 examined. 



Form of colony. The regular alternation of uni- and bi-zooecial internodes is 

 broken in the terminal part of the principal branches by two or three bizooecial 

 internodes succeeding each other (2, 2, 1, 2, 2, 1 or 2, 2, 2, 1 . . . .). 



Of this species I have examined some fragments from Port Western. 



Besides the four, above-described species which show a number of agreements 

 with Sciiticelta margaritacea, it seems, that the following tertiary species described 

 by Mac Gillivray' must be referred to this genus, viz. Catenicella lineata. Cat 

 latifrons and Claviporella longicoUis. • 



Cribricella n. g. 



The sternal area has numerous, scattered pores, of which the outermost are 

 disposed in a distinct curved line, and a small, transversely oval cryptocyst 

 lamina on its inner surface. The hinge-teeth are rudimentary or indistinct and 

 never projecting freely in the aperture. The occlusion takes place in a way similar 

 to that in Scuticella. 



' 76, p. 14, 15, 21. 



