168 



bulletin: museum of comparative zoology. 



Ptychodiscus carinatus, sp. nov. 



Plate 1, Figs. 8, 9. 



A small disk-shaped species with concave anterior and posterior faces, wide 

 furrow and ventro-posterior keel with the longitudinal furrow on its edge. 



Body low, flat, disk-shaped, its length, including the keel, 0.33 of the trans- 

 diameter, which equals the dorso-ventral diameter. Excluding the keel the 

 length is less than 0.25 of the diameter. The epitheca is a circular disk, 

 notched ventrally, with concave anterior face, and broadly rounded edges 

 which pass over into the large transverse furrow. 



The hypotheca is also circular, disk-shaped, with somewhat concave poste- 

 rior face. It is smaller than the epitheca, its diameter being about 0.9 of that 

 of the epitheca. The hypotheca bears a thin ventral keel passing in a radial 

 position from the centre of the posterior face to the flagellar pore. Its height 

 is greatest about one third of the length from the centre, and is about 0.16 of 

 the diameter. It bears the linear longitudinal furrow on its ventro-posterior 

 edge. 



The girdle is very wide with rounded edges, is deeper laterally than dor- 

 sally, is wider proximally than distally, so that a slight descending right spiral 

 with little displacement is present. The longitudinal furrow lies in the ven- 

 tral depression of the keel, is elliptical in outline on the epitheca, where it 

 extends 0.6 of the distance to the centre. 



Surface without sutures, pores, or reticulations. Figure sketched from life. 

 Material in formalin is somewhat less depressed. 



Length, 28 p ; transdiameter, 90 /x. 



Station, 4722. 



Steiniella inflata, sp. nov. 



Plate 3, Fig. 15. 



A large hyaline species with robust body and with anterior end of longi- 

 tudinal furrow bifurcated, very narrow girdle, and broad intercalary bands 

 along sutures. 



The body irregular and asymmetrical, its length 1.1 times the dorso-ventral 

 and 1.2 times the transdiameter, its epitheca conical, deflected to the left, and 

 rotund ventrally, the right side more rotund than the left. Its altitude 0.6 

 of the transdiameter. Apical pore in right margin of longitudinal furrow 

 which passes beyond the apex. 



Hypotheca larger than epitheca, its total altitude 0.7 of the total length and 

 0.8 of the transdiameter. Antapex asymmetrical, broadly rounded, longer upon 

 the left side, with broad ventral excavation. 



Girdle narrow, ribbed, slightly impressed, with prominent margins, forming 

 a descending right spiral with displacement five times its own width. Both 

 proximal and distal ends curved posteriorly, the latter more than the former. 

 Longitudinal furrow passing nearly one fourth of the distance beyond the apex 





