MTZOSTOMIDA 



321 



FAMILY 2. HERPOBDELLIDAE. 



Body subcylindrical, elongate with 3 unarmed muscular ridges in 

 place of jaws; crop without lateral pockets: several genera. 



1. HERPOBDELLA Blainville (Nephelis Savigny). Body long and 

 narrow and with smooth margin; segments contain 5 rings each; genital 

 orifices separated by 2 or 3 rings: many species; on plants and on the 

 under side of stones in streams. 



H. punctata (Leidy) (Fig. 504). Body up to 10 cm. long and 1 cm. 

 wide; color brownish-black with 4 longitudinal rows of irregular black 

 spots ; 3 pairs of eyes : common in streams and pools. 



H. (Dina Blanchard) fervida (Verrill) (Fig. 505). Body up to 5 

 cm. long, variegated pale red in color; 3 or 4 pairs of eyes: abundant 

 in the Great Lakes region. 



CLASS 4. MYZOSTOMIDA.* 



These animals are small disc-shaped parasites of crinoids, ophiurans, 

 and starfishes, on the bodies of which they live either in cysts or free. 

 The body is oval in outline, much flat- 

 tened, and externally unsegmented. It 

 possesses, however, five pairs of para- 

 podia, each of which is stiffened by 

 two setae, and four pairs of latero- 

 ventral sucker-like organs which are 

 probably sense organs. The edge of 

 the body is serrate in some species ; in 

 others ten pairs of short cirri extend 

 from it. A distinct head is not pres- 

 ent (Fig. 506). 



The body cavity is obliterated by 

 the growth of a vascular parenchyma 

 throughout it. The mouth is ventral 

 in position and near the anterior end 

 of the body ; it opens into the pharynx, 

 which forms a proboscis. The intestine is straight and sends out a num- 

 ber of long branches on each side. The anus is near the hinder end of the 

 body. Special vascular and respiratory organs are wanting ; nephridia are 

 present. The nervous system is highly specialized. It consists of two 



* See "Verzeichniss der von den U. S. Coast Survey Steamers Hassler und Blake, 

 von 1867-1879, gesammelten Myzostomideen," by L. von Graff, Bull. Mus. Comp. 

 Zool., Vol. 11, p. 125, 1883. "The Sexual Phases of Myzostoma," by W. M. Wheeler, 

 Mitt, aus d. Zool. St. zu Neap., Vol. 12, p. 227, 1896. "New Marine Worms of the 

 Genus Myzostoma," by J. F. McClendon, Proc. U. S. Nat. Mus., Vol. 32, p. 63, 1907. 



Fig. 506 Diagram of a myzostomid 

 (von Stummer). 1, mouth ; 2, cirrus ; 

 3, parapodium ; 4, lateral sense organ ; 

 5, intestinal branches ; 6, ovary ; 7, 

 nephridium ; 8, uterus ; 9, stomach ; 

 10, cloaca ; 11, anus ; 12, male genital 

 pore. 



