STROPHOMENIA AGASSIZI. 229 



other passes beneath the duct and forms a commissure. No signs of ganglia 

 exist along this ventral commissure, and accordingly there are no indications 

 that it forms a subradular system as might be suspected from its position. 

 The labiobuccal ganglia are also united by the usual commissure crossing over 

 the dorsal surface of the radula. 



In the posterior end of the body both the lateral and pedal ganglia terminate 

 in well-defined enlargements which are united in typical fashion by connectives. 

 A few small nerves from the pedal enlargements extend posteriorly and become 

 lost in the somatic musculature. In addition to the suprarectal commissure 

 the posterior end of each lateral gangUon gives rise to two main nerve bundles 

 whose ultimate ramifications form a plexus over a considerable portion of the 

 posterior end of the animal. Only a small portion of this network has been 

 followed in detail, but there are indications that it exists beneath the somatic 

 musculature, behind the level of the posterior end of the pericardium. Small 

 ganglionic masses occur at the nodal points. It may be added that this net 

 extends across the mid-dorsal hne, at least in the neighborhood of the dorso- 

 terminal sense organ, thus forming a species of suprarectal commissure though 

 of a diffuse type. A careful examination of the nerves innervating the dorso- 

 terminal sense organ shows that they have their origin in the more anterior of 

 the dorsal commissures, which accordingly corresponds to the usual one in 

 neomenians generally. Simroth mentions two dorsal commissures in Pro- 

 neomenia but as no figure is given a further comparison is not possible. 



Strophomenia agassizi, sp. nov. 



Five specimens of this species were dredged southeast of Nantucket, Mass. 

 (Sta. 2046 A) at a depth of 407 fms., and four additional specimens were taken 

 to the northeast of this point (Sta. 2528A) in water 677 fms. deep. In every 

 case the animal was coiled about the branches of an alcyonarian coral, Acantho- 

 gorgia armata. Two of the specimens from Sta. 2046A are in the act of copula- 

 tion, the posterior ends being appUed to each other so that the cloacal openings 

 are in communication with each other (Plate 1, fig. 1). In alcohol the color 

 is light brownish yellow. The largest specimen is 37 mm. in length and 1.5 mm. 

 in average diameter, while the smallest is 22 mm. long and 1.1 mm. in thickness. 

 In the only specimen sectioned two dorso-terminal sense organs are present 

 (see section on nervous system). 



The cuticle surrounding the body measures, along the sides of the 

 animal, approximately 0.19 mm.; along the dorsal side it is shghtly thicker. 



