231 



Scuticella margaritacea, var. fissurata n. 



(PI. XX, figs. 3 b, 3 e). 



This form, which may for the present be regarded as a variety, differs from 

 the main form in the following characters. The relatively large sinus is bounded 

 by two short, broad, hollow spines, which are open at the end and which form 

 the greater part of the proximal margin of the aperture. The mother-zooecium 

 of the bizooecial segment has a slit-like, adzocecial, infra-scapular chamber. The 

 frontal surface of the gonozooecium is on either side provided with two rounded 

 lateral chambers, and its aperture has a well developed, rather deep sinus, which 

 like the zocecial aperture is bounded by two short, broad, hollow spines open at 

 the end. The ooecium lacks the two groups of closely situated pores, and the 

 kenozooecium has at its top a high avicularium, which communicates with two 

 unequally large, partially membranous lateral chambers. 



Of this form I have examined colonies from Port Phillip, Australia. 



Scuticella urnula Mac Gilliv. 

 Catenicella urnula Mac Gillivray, Transactions and Proceedings of the Royal 



Soc. of Victoria for 1886, Vol. XXIII, pag. 34, PI. I, figs. 2, 2 a, 1887. 

 (PI. XX, figs. 1 a-1 e, PI. XI, figs. 4 a, 4 b). 



The zooecia large, rhombic-oval with a longitudinally rounded aperture, 

 bounded by a concave proximal margin. The long, oval sternal area is provided 

 with 5—7 pear-shaped fenestrae and with a long, tongue-shaped cryptocyst lamina, 

 which often reaches the starting point of the proximal fenestra. The compara- 

 tively large, deep, sternal sinus is occupied by 2—5 ribs or spines, of which the 

 two distal are very high and the proximal, when occurring, are very small and 

 tubercle-shaped. 



The lateral chambers. The scapular chamber is in most zocecia developed 

 as a good-sized, more or less complete avicularium with the aperture frontally 

 directed and in the complete state with a short and broadly triangular mandible. 

 It is, chiefly, on account of its arched outer wall, well separated from the zoce- 

 cium, and the pointed lamina springing from its top, which forms" the outer wall 

 of the supra-scapular, for the rest membranous chamber, gives it a certain likeness 

 to the lobe of an ear in a mammal. On the adzocecial surface of the daughter- 

 zooecium it is a low membranous cavity, which, apart from a separating line 

 but partly developed, has fused with the corresponding chamber of the mother- 

 zooecium. The scapular chamber is often more or less incompletely developed on 

 one or on both sides of a greater or smaller number of the zocecia succeeding 



