24 Papers from the Marine Biological Laboratory at Tortugas. 



muscular, and lies parallel with the cirrus-pouch on its left side. The 

 ova are long-elliptical in outline, the longer diameter being more than 2.5 

 times the shorter. Each ovum is provided with a single filament at one 

 pole. In a few cases there appeared to be a filament at the other pole, 

 but in these cases the second filament did not appear to be a prolongation 

 of the shell as in the ordinary cases. The body -wall is thickly beset with 

 small, granular clusters which give a mottled appearance to the surface 

 of the specimen in balsam. These may be clusters of yolk-forming cells. 



Host, Caretta caretta: July i, 1906, one specimen. 



Dimensions in balsam: Length 4.60; breadth 1.33; oral sucker, 

 length 0.34, breadth 0.38; posterior pit o.io; ova 0.029 by o.oii; length 

 of ovum and filament 0.12. 



Distomum sp., immature, related to genus Calycodes. (Figs. 4-6.) 



The following description is based on a single immature specimen: 

 Body linear, rather stout ; at the anterior end there is a deeply emarginate 

 flap which is muscular and a continuation of the wall of the oral sucker. 

 This flap projects ventrally and overhangs the mouth like an upper lip. 

 There appear to be 4 low, lateral papillae on the head, one of each pair 

 being the lateral angle of the upper lip; oral sucker nearly twice the 

 diameter of the ventral sucker; pharynx moderate, pyriform; esophagus 

 long; bifurcation of the intestine at the ventral sucker which is situated 

 a little back of the middle of the length of the body. The intestinal rami 

 are thick- walled and extend to the posterior end of the body. The speci- 

 men is too immature to permit of satisfactory identification of the rudi- 

 ments of the genitalia. The genital aperture is at the anterior border 

 of the ventral sucker. Two small bodies, median, and near the posterior 

 end are probably rudiments of the testes. In front of the anterior of these 

 there is another small body which presumably represents the ovary. 

 In front of the latter there is a spiral tube which reaches to the ventral 

 sucker and doubtless is the uterus. 



Host, Caretta caretta : July 4, 1907, i specimen, immature. 



Dimensions, life: Length 1.50; breadth 0.45; oral sucker 0.30; 

 pharynx 0.08; ventral sucker 0.17; breadth of head 0.33. 



Dimensions in balsam: Length 1.40; breadth 0.43; length of neck 

 0.66; oral sucker, length 0.24, breadth 0.28; pharynx, length o.io, 

 breadth 0.08; ventral sucker, length 0.14, breadth 0.15. 



Pachypsolus ovalis sp. nov. (Figs. 7-14.) 



Under moderate magnification this species appears to be smooth, 

 but when more highly magnified it is seen to be covered by a peculiar 

 layer consisting of slender, rod-like structures embedded in a fine gran- 

 ular matrix. This layer is rather thick and has a tendency to separate 

 from the underlying layer, or to disintegrate. A sketch representing^ 

 the species as spinose would be misleading. In cases where this layer 

 has partly disintegrated the outline left often presents the appearance 

 of being beset with slender rod-like or cilia-like structures. Indeed the 

 layer when intact is not unlike in appearance to a ciliated surface. The 

 most obvious difference between this species and P. irroratus (R.) Looss is. 



