890 EEPORT OF COMMISSIONER OP FISH AND FISHERIES. [12] 



from any other in the family. The nearest allied one is evidently Psam- 

 moryctes ; but this genus has large and distinctly fan-shaped spines, 

 which are entirely wanting in Hemitubifex. As yet only one species 

 known, viz: 



Hemitubifex insignis n. sp. 



(Pis. VII aud VIII ; Fig. 6.) 



Nervous system. — The cephalic ganglion is nearly square. Its anterior 

 margin is deeply concave ; the lobes of the posterior margin are well 

 rounded, aud the sinus between them deep and narrow (Fig. Qg; PI. 



yiii). 



Generative system. — The efferent duct is about one-half longer than 

 the atrium and penis together. The atrium is comparatively narrow, 

 except its upj)er part, which is globular, forming a "vesicula sem- 

 inalis," upon which the prostata is grafted. This globular part of the 

 atrium is of exactly the same consistency as the lower part of the 

 atrium itself, and differs in this respect from Fsammoryctes, which 

 genus is said * to have a non-glandular atrium proper. The globular 

 chamber of the atrium can more properly be called a receptacle for the 

 mucus of the prostata gland, when it is mixed with the spermatozoa, 

 descended from the efferent duct. The penis proper is extraordinarily 

 large, thickest a little below its base, aud frOm here gradually tapering 

 towards the exterior apex, which, however, is somewhat swelled and 

 rounded. The penis sheath is chitinous and covers only a part of the 

 I)enis, leaving the swelled apex and the larger portion of the upper part 

 uncovered. The oviduct is double, both its sheaths being chitinous, 

 funnel-shaped, aud about twice as large as the i)enis sheath (Fig. Qc, 

 ovd). Numerous muscles are attached to the interior upper surface of 

 the oviduct and penis proper, binding them to the interior of the body 

 wall. The receptacle is supported by a long, narrow stem, at the base 

 of which are several wing-like glands. The spermatophores are thick 

 and short, generally bent, each one surrounded by a pellucid membrane 

 (Fig. Gh). 



The segmental organs are long and narrow. The interior aperture is 

 surrounded by two nearly equal lobes; no inflated cells and no enlarged 

 chambers, as in Spirosperma. 



The integument is very smooth, and the body of the worm resembles 

 much that of LimnodrUus or Tuhifex. The spines are of two kinds, 

 hair-spines and forked spines. The latter are regularly dispersed two 

 and two in each fascicle, except on the upper or dorsal side of the body, 

 where we occasionally also find a few hair-siDines. The distribution of 

 these is very irregular. In one specimen they were found in the third, 

 fourth, seventh, twelfth, and thirteenth segments, but even here not in 

 all the upper fascicles. In another specimen from the same locality I 



' Vejdovsky, Zeitsch.. f. w. Zoolosie; Bd. XXVII, page 138. 



