10 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 123 



Relationships. — In Poulsen's (1965, p. 316) key to the Astero- 

 pinae (=Cylindroleberinae), P. pollex falls between Diasterope and 

 Parasterope. The female sensory bristle of the adult female 1st an- 

 tenna has 6 long terminal filaments as in Parasterope, whereas the 

 tip of the ventral branch of the mandibular coxale endite has several 

 marginal spines, which makes it resemble more closely the coxale 

 endite of Diasterope than of Parasterope. In order to include the 

 species in Parasterope, it is necessary to expand the diagnosis given 

 by Poulsen (1965, p. 362) to include species having several small 

 spines near the tip of the ventral branch of the coxale endite. 



Specimens interpreted as being male N-l instars of P. pollex have 

 a short proximal filament on the sensory branch of the 1st antenna. 

 This character places the species close to the genus Diasterope and 

 indicates the importance of having adult females available when 

 classifying members of this subfamily. 



Cypridina mariae Baird, 1850, was designated by Sylvester-Bradley 

 (1961, p. 402) as the type-species of Cylindroleberis, which is the 

 type-genus of the family Cylindroleberidae. The structure of the 

 appendages of the unique holotype of Cypridina mariae from the Isle 

 of Skye is unknown. Although the species has been identified from 

 many areas by others, the identifications include several species and 

 genera (see discussion by Skogsberg, 1920, pp. 518-522). Therefore, 

 it is not possible to determine with certainty the genus in which the 

 type-species belongs. Because of the relative instability of generic 

 names in the family, especially in the subfamily Cylindroleberinae, 

 the assignment of P. pollex to the genus Parasterope must be pro- 

 visional. 



Description of adult (figs. 4-6, 7a-d; pi. la, b). — Female shell (figs. 

 4a, b, d-j; pi. la, b) : In lateral view oval, elongate, with greatest 

 height slightly behind middle; in dorsal view with greatest width 

 about midway between middle and posterior end; anterior and 

 posterior margins evenly rounded; lateral surface smooth, with 

 scattered normal pore canals, some with short hairs; incisur deep, 

 narrow, with upper margin overlapping lower proximally; inner 

 lamella with 40 to 42 medial bristles above incisur, 21 to 35 bristles 

 below incisur, and about 10 bristles along ventral inner margin; 

 medial ridge anterior to posterior margin with broad blunt spines in- 

 terspersed with minute spines; about 27 spines in row between medial 

 ridge and posterior margin; radial pore canals numerous, false radial 

 pore canals sparse, containing hairs along posterior margin of shell; 

 selvage narrow with fringe of hairs along anterodorsal margin; ad- 

 ductor muscle scars obscure, consisting of ovoid scars in cluster near 

 middle of valves. 



