1894.] NATURAL SCIENCES OF PHILADELPHIA. 451 



Fig. If, a longiti'dinal section uear the median line of the dorsal 

 organ of somite VIII; a, intermuscular spaces. X 500. 



Fig. Id, section of a terminal portion of a dorsal appendage. 

 X 640. 



In this species, which is described from sections and specimens 

 mounted entire, the body is terete throughout, or owing to the in- 

 crease in thickness of the dorsal walls of the major annuli, appears 

 somewhat compressed at these points. The somites VI, VII, and 

 VIII are of about equal diameter, those anterior and posterior to them 

 tapering respectively toward the head and caudal disk. Bi-annula- 

 tion of the body somites is very marked. The head is rather slen- 

 der, and consists of a circum-oral anuulus divided into thick entire 

 dorsal and ventral lips, and two similar post-oral rings. The caudal 

 sucker is a muscular disk of simple form, and about the diameter of 

 the 1st post-cephalic somite; its axis coincides with that of the body 

 somites. 



Dorsal organs are highly developed in this species on post-cephalic 

 somites III, IV, V, and VIII. Somites VI and VII, and in less 

 degree, II also, exhibit slight dorsal thickenings of the body muscu- 

 lature. On the dorsum of the major aunulus of somite III the 

 body walls rise into a high compressed transverse ridge or plate, 

 which fades out on the sides of the somite, and is produced laterally 

 into a conspicuous, forwardly projecting trilobed wing, the anterior 

 division of which flares outward and extends far forward over 

 somite II, usually ending in a slightly bifid expansion. The remain- 

 ing lobes are simple conical tines, which project upward and slightly 

 outward. The two wings flare so strongly that the distance be- 

 tween their apices is about Ih times the diameter of the somite. 

 Their shape is very strongly suggestive of the antlers of a young 

 moose, hence the name given to this species. The generic name was 

 also suggested by this species, in which the dorsal organs have a 

 wing- like aspect not seen in the other species. 



The dorsal appendage of the Vlllth somite is also highly de- 

 veloped, and similar to the one just described. Its lateral wings, 

 however, are less conspicuous, and are directed posteriorly instead of 

 antei'ioi'ly, and also flare outwai'd more conspicuously. The whole 

 organ is strongly concave behind, while that on the Ilird somite is 

 similarly concave before. A small gland, closely resembling a clitellar 

 gland, is sometimes present (in two out of three series of sections) 



