508 A. E. Verrill — Marine Plariarians of Xeiv England. 



it may be near the middle of the ventral side, or even behind the 

 middle. It is often large and is sometimes simple, but more fre- 

 quently it is surrounded by a slightly developed muscular ring or 

 collar ; moi*e rarely there is a rudimentary pharynx. The integu- 

 ment is generally filled with clusters of rhabdites. There is often a 

 peculiar glandular frontal organ opening at the anterior end. 



The brain, longitudinal nervous trunks, and nervous branches are 

 present, but not so well-defined as in the previous groups. A pair 

 of ocelli may be present, but are oftener absent. A median otocyst 

 is almost always present. Posterior tentacle-like organs or cii'ri 

 are sometimes present. 



The reproductive organs are variable in structure and position. 

 Sometimes there is but a single genital pore, but usually there are 

 two median ones, posteriorly situated, the male orifice being be- 

 hind the female. The ovaries are usually lateral and paired; special 

 yolk-glands are not developed. A bursa seminalis or spermatheca 

 may be present, or absent; sometimes there are two. The testes 

 are folicular and imbeddeJ in the parenchyma. The penis may be 

 simple or armed; a seminal vesicle is usually present. Eggs are 

 usually enclosed in capsules. 



The external form is exceedingly varied. Many species are flat, 

 broad-elliptical or ovate ; others are long and narrow ; some are 

 nearly terete; others are angular in outline. Some species [Convo- 

 luta) habitually curl the sides of the body inward and downward, 

 so that they appear narrower than they really are. The size is 

 generally small, the colors often bright. 



Family, Aphanostomidje Graff, Monog. 



Body usually more or less flattened, elliptical, ovate, or cordate, 

 long or short, frequently with the sides curved downward. Mouth 

 ventral, behind the otocyst, often median or submedian. Pharynx ru- 

 dimentary or wanting. Otocyst present. Ocelli sometimes two, often 

 absent. Genital orifices separate. Penis simple, unarmed. Bursa 

 seminalis well-developed, with one, two, or several tubular outlets. 



Aphanostoma (Ersted. 



Kroyer's Naturhist. Tidssk., ser. 2, vol. i. p. 417, 1845; Carus, Fauna Med., p. 139, 



1884; GrafE, Monog., p. 220; Graff, Turbell. A.ccela, pp. 55, 59, 1891. 

 Aphanostomum Jensen, Turbell. Lit. Norvegue, p. 22, 1878. 



Body more or less flattened, oblong, ovate, or elliptical ; usually 

 narrowed posteriorly. Mouth circular, before or near the middle. 



