418 On the Genus CrassicauJa. 



but it is impossiblo to settle definitely at present which 

 records refer to wliicli species, except as regards those dealt 

 with in the present paper. 



'I'here seems to be reason for believing that yet a third 

 species of Crassicauda may exist, ditiering tVoni the two 

 already considered in the size and structure of its egg^, and 

 probably in other particulars. In 1916 Mr. Bennett sent to 

 the ]\[nseum some fragments, in poor condition, of what 

 appeared to be a species of this genus, from the kidney of a 

 Uiiperoodon, from the South Orkneys. The fragments 

 contain immense numbers of ova (fig. 6, B, C) of a larger size 

 (66 /iX 33 yu.) than those of C. crassicauda and C. boopis, and 

 of characteristic structure, in that the shell, in the fully- 

 formed condition, has a thickened belt of chitin round the 

 middle region, the ends being comparatively thin-shelled. 



The following brief generic diagnosis may now be given 

 (it being borne in mind that no complete account yet exists 

 of any species) : — 



CuASSlCAUDA, Leiper and Atkinson, 1914. 



Filariidai (?) : ]\Iouth without lips, but with one small 

 papilla and three larger, more lateral papillre on either side * ; 

 cuticle thick, transversely striated, sometimes raised into a 

 swelling which appears to act as a " holdfast." Male with 

 laterally compressed and spirally coiled tail, with a ventral 

 groove behind the cloaca ; at either side of the groove a 

 somewhat irregular row of genital papillae ; two small unequal 

 S|»icules present, or spicules absent. Female with vulva near 

 the posterior end of the body, in a constriction just in front 

 of the knob-like caudal extremity ; vagina very short ; uteri 

 two, parallel ; anus terminal ; ova with thick shell, con- 

 taining a coiled embryo at the time of laying. 



llab. Various parts of the urinogenitai system (or, excep- 

 tiouidly, other parts of the body) of Oetacea. 



Genotype : C. crassicauda (Creplin, 182i*) [nee C. crassi- 

 cauda (Crepl.) of Leiper and Atkinson, 1914 t^ 1915J. 



Two species may at present be distinguished with some 

 certainty, though their characters are as yet incompletely 

 worked out, and the determination must depend upon measure- 

 ments when male tails are absent : — 



1. Crassicauda crassicauda (Crepl.). 

 Two unequal spicules present in the male. Thickness of 



* See Bftvlis, 1«](3. 



