24(5 



Pterocella n. g. 



The steriKil area has ;{ — 7 fenestra! disposeti in a curve and a rouiuled ervplo- 

 cysl lamina on its inner surface. The ajierture, tlie |)()sterior part of which is 

 Irapeziforni or arch-shajied, is provided willi Iwo slroni;ly developed, IVeely jiro- 

 jecting hinge-teeth. The lateral chainhers form a wing-like marginal portion on 

 either side in the whole length of the zo(L'cium. The molher-zoo'cium has a small 

 (ii)icnl(triniii on its adzod'cial side. The occlusion lakes place in a way similar 

 to that in Sciilicclld. 



Pterocella alata Wyv. Thompson. 

 Catenicella alata \\'yv. Thompson, Nat. Hist. He\ie\v, ISfjiS. 



Proceed. Dublin Univ. Zool. and IJolan. Associat. I, pag. 80, 

 PI. VI. fig. 4. 

 (PI. XII, (ii^s. fia, 01), pi. XXI, Ri;. 1:0. 



The zocecia oval with a nund)er of very small seatlered ])ores and a very 

 strongly arched basal surface with undulating, longitudinal stria-. The sternal 

 area, which is of about Ihe same size as the ajjcrture, is provided willi 1— (> 

 round or oval fenestra;, Ihrough which the margin of Ihe inner calcareous lamina 

 can be clearly seen. The plainly visible frontal sinus is <)ccu])ied by 1 'A jiroxi- 

 mal, rudimentary or veiy slightly develojied spines and further by the two large, 

 distal ones which meet in a sulin-al line. The two latter sometimes show a small 

 inner ca\ity. The anter of the aperture is semi-eliiplicaj, and its |)osler has a 

 straight median j)ortion and two lateral parts oblicjnely ascending towards the 

 hinge-teeth. 



The lateral chambers form on eilher side a dislally directed, rounded, tri- 

 angular expansion, the lop or the j)oint of which lies at the end of the su])ra- 

 scapular chamber. The distance between the ends of llie two scapular chambers 

 is in a unizocecial internode about the length of the inlernode, and the two 

 lateral expansions form a distal angle of 120" — 140" with each other. The 

 scapular chamber, which is everywhere developed as an avicularium with an 

 extremely small mandible, has the form of a long, compressed lube, and con- 

 trary to the case in all the above-described species an avicularium api)ears also 

 on the adzoa'cial side of the mother-zoa'cium, where it is situated oj)j)osite the 

 distal part of the aperture. It is here however considerably shorter and stands 

 out almost vertically from the surface of Ihe zoociuin. The wing-like expansions 

 formed by the lateral chambers are widest in the supra-scapular chand)er, from 

 which they decrease in breadth proximally. The su|)ra scapular chand)er, which 



