OSTEAOODA. 638 



Lcperditia.J 



Order OSTRACODA. 



Family LEPERDIITID^. 



Genus LEPERDITIA, fionault. 



Leperditia, Ronault, 1851, Bull. Soo. G«ol., France, 2d Ser., vol. 8, p. 377; Fr. Schmidt, 1873, Mem. 



Acad. Imp. Sci. St. Petersburg, vol. 21, No. 2; also 1883, idem, vol. 31, 

 No. 5; Jones, 1881, Ann. Mag. Nat Hist., 5th ser., vol. 8, p. 332; 

 Jones and Kiekby, 1887, Proc. Geol. Assoc, vol. 9, p. 503. Also Jones, 

 1856, 1858, 1884, 1890,1891; Kolmodin, 1869 and 1879; Krausb, 1877 

 and 1891; Kiesow, 1884; Zittel, 1885; Mili^ek, 1889; Ulkich, 1890 

 (not 1892). Previous to 1851 species were referred to Gytherina, Cytliere 

 and Cypridina. 



Carapace more or less convex, often large, suboblong or semiovate in outline, 

 with an oblique backward swing; dorsal edge straight, often angular at the extrem- 

 ities; ventral outline rounded, sometimes a little produced at the middle; greatest 

 thickness in the ventral half, the lower edge usually being also blunt; valves unequal, 

 the right the larger and overlapping the left; overlap chiefly ventral, simple, or the 

 further entrance of the ventral edge of the left valve is prevented by two or more 

 papillae set within the overlapping edge of the right; hinge simple. Surface fre- 

 quently horny in appearance, smooth in most cases, granulose or minutely punctate 

 in others; a small tubercle or "eye-spot" is generally present on the antero-dorsal 

 fourth, and a large, rounded subcentrally situated sunken muscle-spot is seen on the 

 inner side of the valves and not infrequently distinguishable on the exterior also. 



Type; L. brittannica Ronault. 



An excellent account of this genus is given by Dr. Fr. Schmidt {he. cit.) in his 

 two papers on the "Russichen Silurichen Leperditien." According to that author 

 and to Roemer, L. grandis Schrenck {L. gigantea Roemer) attained a length of 43 mm. 

 This is the largest species of the genus and probably the largest known ostracode. 

 In most of the species the length varies between 8 mm. and 25 mm., while in several 

 other unquestionably congeneric forms the maximum length is less than 4 mm. 

 Besides, a number of minute forms are referred here by Prof. Jones, myself and 

 others, of which it is at least doubtful that they really belong to the genus. Because 

 of their small size and chiefly perhaps because of the imperfection of the specimens, 

 the ventral overlap of the right valve has not been established for them. Nor has 

 the "eye-tubercle" and other peculiarities of the typical species been seen on them. 

 For some at any rate Aparchites would offer a more natural reception. Finally, 

 a number of comparatively small species (1.5 mm. to 3.0 mm.) which I have here- 



