248 



Pterocella carinata Busk. 



Catenicella carinata Busk, Voyage of Rattlesnake, I, pag. 363, Catalogue of Marine 



Polyzoa, Cheilostomata, pag. 12, PI. VI, figs. 4, 5, 6. 



(PI. XII, fig. 5 a). 



The zocecia quadrangularly oval, of a rounded triangular transverse section, 

 the basal surface consisting of two lateral halves meeting at an acute angle. 

 This surface has slightly undulating, longitudinal strise and is provided with a 

 low median ridge, which in its centre rises into a triangular, spine-like process. 

 The sternal area is generally smaller than the aperture and provided with 3 

 fenestrse, and the extremely small frontal sinus is occupied by two rudimentary 

 spines. The anter of the aperture is semi-elliptical and its poster concave. 



The lateral chambers form on either side a triangular, acute-angled expan- 

 sion, which is directed sometimes straight outwards, sometimes a little distally 

 and the vertex or point lies at the end of the scapular chamber. The distance 

 between the ends of the two scapular chambers is in an unizooecial internode 

 larger nearly by a half than the length of the internode, and the two lateral 

 expansions form a distal angle of 180" — 270" with each other. The scapular 

 chamber has an extremely small mandible and is shaped like a long, narrow, 

 compi'essed tube, and the two adjoining, triangular chambers have each a large, 

 pear-shaped opening, which is larger in the supra-scapular chamber, the frontal 

 and distal walls of which are uncalcified in their inner half. The pedal chamber 

 has a long, oval opening. The mother-zooecium in the bizooecial internode is pro- 

 vided with a small avicularium, and proximally to the latter we find as in P. alata 

 a narrow boundary chamber. 



The ocecium. The ooecium as well as the gonozocecium and the covering 

 zocecium bear a close resemblance to the corresponding parts in P. alata and I 

 shall accordingly limit myself to pointing out the most important differences. On 

 the gonozocEcium the sternal sinus is much less developed and occupied by two 

 likewise slightly developed spines, which, however, also have a terminal part bent 

 inwards and proximally. The most conspicuous difference is however found in 

 the covering zocecium, which is provided with two large fenestrse separated by 

 a rather broad longitudinal belt. 



Form of colony. In the small fragment from Napier, New Zealand, that I 

 have examined, two bizooecial internodes nowhere succeed each other. 



