MUSEUM OF COMPARATIVE ZOOLOGY. 19 



tomus has a very short bulbus and two rows, and Heterodontus francisci 

 has three rows in a bulbus httle if any more than half as long as the 

 ventricle. Selache has three rows in a bulbus equally short (see Pavesi, 

 Del Genere Selache, PI. III., aS*. rostrata). A specimen of Somniosus 

 microcephalus has a short bulbus and four rows of valves. 



Behind the ventricle, in the partition, between the peritoneum and the 

 pericardium, there is a spongy mass of dark tissue an eighth of an inch 

 in thickness. 



A Cardiac Parasite, Tetrarhynchus wardii, sp. n. 



The worm figured .on Plate XVIII. figs. 8-10, was found within the 

 cardiac chamber, attached to the lower side of the auricle, between it 

 and the ventricle and bulbus. Dr. E. L. Mark, to whom it was sub- 

 mitted, pronounces it a Tetrarhynchus, and thinks it possesses characters 

 which will not admit of placing it in any of the described species of the 

 genus. The head is large, subelliptical in transverse section, and sub- 

 quadrangular or oblong in longitudinal outline. Against the scalpel or 

 needle it is as hard as bone. The groove on each side extends back half 

 the length of the head. When the hardened mucus is removed, the sur- 

 face is seen to be covered with small papillae. Some of the teeth are 

 much curved, forming arcs of ninety degrees ; others are a little nearer 

 straight. All seem to be compressed, and the base extends under the 

 cusp or claw nearly the length of the latter. 



The slender portion, or tail, in a measure resembles the flattened tails 

 of certain angle-worms. It does not show marks of division into seg- 

 ments. Entrance into the cardiac chamber must have been effected when 

 the worm was small, for at present the walls seem entirely closed against 

 intruders. 



Being indebted to Professor Ward for our knowledge of it, we have 

 taken the liberty of introducing the species in his name. 



Ovaries and Oviducts. 



Plate XIX. Fig. 1. 



Fortunately for us, when the captor tore the viscera from the speci- 

 men he left several important pieces. A section of some twelve inches 

 in length of the ovaries and oviducts is represented in the sketch. The 

 ovaries had been badly preserved and were much torn. Three inches 

 from the anterior opening of one of the oviducts it bore a nidamental 

 gland ; the gland of the other tube was an inch farther back. A piece 



