418 On the Genus Crassicauda. 
but it is impossible to settle definitely at present which 
records refer to which species, except as regards those dealt 
with in the present paper. 
There seems to be reason for believing that yet a third 
species of Crassicauda may exist, differing from the two 
already considered in the size and structure of its eggs, and 
probably in other particulars. In 1916 Mr. Bennett sent to 
the Museum some fragments, in poor condition, of what 
appeared to be a species of this genus, from the kidney of a 
Hyperoodon, from the South Orkneys. The fragments 
contain immense numbers of ova (fig. 6, B, C) of a larger size 
(66 wx 33 w) 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) :— 
CrASSICAUDA, Leiper and Atkinson, 1914. 
Filariide (?): Mouth without lips, but with one small 
papilla and three larger, more lateral papillee 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 papille ; two small unequal 
spicules present, or spicules absent. emale 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. 
Hab. Various parts of the urinogenital system (or, excep- 
tionally, other parts of the body) of Cetacea. 
Genotype: C. crassicauda (Creplin, 1829) [nee C. crassi- 
cauda (Crepl.) of Leiper and Atkinson, 1914 & 1915). 
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 Baylis, 1916. 
