KNOWN SPECIES OF MARINE OSTRACODA. 361 



their characters that it would be very satisfactory to be able without misgiving to 

 place them in a distinct genus. But the characters which have been proposed for the 

 genus Cythereis slide so insensibly, and through so many osculant forms, into Cythere, 

 that I have found it almost impossible, in many cases, to determine to which genus a 

 particular species ought to be referred. Cythere septentrionalis, C. costata, C. cristatella, 

 &c., may be taken as examples of these debateable forms. Under these circumstances, 

 there seemed to be but two reasonable courses open to me — either to reject the genus 

 altogether, or to restrict it by some arbitrary line to the conspicuously fimbriated, 

 spinous, and quadrilateral species so well represented by C. jonesii. I have chosen the 

 latter course as being, on the whole, of the greater practical utility. A more perfect 

 knowledge of the various species, and especially of the anatomy of the animals, will 

 probably in time lead to a better classification. 



Order OSTRACODA, Latreille. 



Family CYPRID^E, Baird. 



Subfamily Cytherin^, Dana. 



Genus Cytherella, Jones (subgenus). 



Generic Characters. — "-4mmaZ unknown. Cara^jace oblong, compressed; smooth or 

 pitted ; no terminal denticulations : contact-margins of the right (larger) valve grooved 

 or rabbeted on its inner edge for the reception of a flange presented by the contact- 

 margin of the left (smaller) valve ; both groove and flange stronger at the posterior 

 than at the anterior portion of the valves." Ludd spots arranged in a curved pinnate 

 series on an oblong, obliquely placed depression near the centre of the shell. The 

 depression appears internally as an elevation or tubercle. The number of the spots is 

 from twelve to sixteen, and in shape they are linear-oblong, increasing in length towards 

 the ventral margin. 



'b' 



1. Cytherella pulchra, n. sp. (PI. LVII. fig. 1, a-d.) 



Carapace elliptic-oblong. Dorsal and ventral margins nearly straight, parallel, slightly 

 sinuated. Extremities rounded. Dorsal aspect ovate-oblong, compressed. Surface 

 smooth, white. Lucid spots near the middle of the ventral half of the carapace, con- 

 sisting of about sixteen linear-ovate spots arranged in a pinnate manner along a central 

 curved line, the larger spots being nearest to the ventral margin ; the whole group is 

 situated in a slight depression of the valves, and is very conspicuous also on the inner 

 surface. 



Length -^ in. ('6 mm.). 



Hab. Australia. 



VOL. v. — PART V. 3 B 



