34: McMURRICH 



directive pairs there are 8 pairs of a fifth cycle regularly ar- 

 ranged and in the interspace lateral to this there are two pairs 

 of the fifth cycle. In each the two interspaces on the other 

 side of the same directives there is a single pair of the fifth 

 cycle, and in the middle lateral interspace of this same side of 

 the body there are 8 pairs of the fifth cycle and in addition 6 rep- 

 resentatives of a sixth cycle. The arrangement in this speci- 

 men is shown in the annexed figure, from which it may be seen 

 that Carlgren's law that the mesenteries of the last cycle develop 

 earliest in the interspaces adjoining the oldest pairs already pres- 

 ent, is complied with. 



The mesenteries of the first cycle are complete throughout 

 the entire length of the stomatodseum ; those of the second 

 cycle are also complete, but are not attached so far down the 

 stomatodseum as the members of the first cycle, while those 

 of the third cycle reach the stomatodaeum only in its upper- 

 most part. The fourth, fifth and sixth cycles are incomplete. 

 All the members of the first two cycles are sterile, the repro- 

 ductive organs being borne apparently by the members of the 

 third and fourth cycles. Both oral and marginal mesenterial 

 stomata are present, the latter usually quite small. 



Finally a word as to the synonymy of the West Coast speci- 

 mens of U. crassicornis. As already stated, Verrill ('69) was 

 the first to correctly identify this species from the West Coast of 

 America, and he records its occurrence in Puget Sound, and in 

 the Arctic Ocean north of Behring Straits, while Murdoch ('85), 

 found it at Point Barrow. Verrill in his list of synonyms in- 

 cludes, with some doubt however, the A. Laurcntii and the 

 A. elegantissima of Brandt ('35) obtained in Behring Sea and 

 at Sitka ; Andres regards these two forms as being species 

 delendce on account of the insufficiency of their descriptions. I 

 believe, however, that there are sufficient grounds for identify- 

 ing the A. Laiirentii with U, crassicornis^ though I think Verrill 

 was probably in error in likewise identifying the A. elegan- 

 tissima with that species, since I have found in the present col- 

 lection forms, described in preceding pages, which seem to 

 agree with Brandt's description. I may say that I made an 



