66-1 RET. T. R. R. STEUB1>'G ON CRUSTACEANS [May 22, 



Fatn. Trichoniscid^. 



1898. Trichoniscidce, Sars, Crustacea of Norway, ii. p. 159. 



1900. TricJioniscidce, H. Kichardson, Am. Nat. xxxiv. pp. 302, 306. 



Id separating this family from the Ligiiclae, Sars assigns to it the 

 genera TricJioniscus, Trichoniscoides, Ilaplophthalmus, Scyphacella, 

 and Actonkcus, while leaving to tlie Ligiidae the genera Lif/ia, 

 Ligidimn, Titanethes, Styloni^cvs, and Stympludns. In the latter 

 family the first antenniie have the third joint minute, the second 

 maxillae have two plumose seta? on the inner margin, tlie maxilli- 

 peds have the terminal part distinctly five-jointed, and the uropods 

 are descrihed as freely projecting behind. In contradistinction to 

 this, in the Trichoniscidse the first antennaj have the third joint 

 well developed, the second maxillse are without plumose setse on 

 the inner margin, the maxillipeds have the terminal part generally 

 imperfectly articulated, and the uropods have the peduncle broadly 

 expanded inside and partly covered by the last caudal segment. 

 There are other distinctions drawn by Sar.s, of more or less import- 

 ance, to one of which it is specially needful to call attention. In 

 the Ligiidse the second antennae have a "multiarticulate flagellum," 

 whereas in the Trichoniscidse they have a " flagellum composed of 

 only a restricted number of articulations." The restricted number 

 is not specified, but apparently it is not intended to exceed four or 

 five, or seven at most. Now both species included by Dana in his 

 genus Stjjlonisciis at its institution have the multiarticulate fla- 

 gellum, which is " seven to ten-jointed " in magdlanictis and " about 

 sixteen-jointed '"' in longistyJis. But magcllanlciis by its maxillipeds 

 and character in general clearly belongs to Triclioniscus. There- 

 fore the distinction between the two families based on the number 

 of joints in the flagellum of the second antennre is no longer tenable. 

 That Styloniscus may still belong to the Ligiidaj is possible. In the 

 Californian species gracilis, added to the genus by Dana in 1856, 

 the flagellum of the second antennce has about fourteen joints and 

 is nearly as long as the two preceding joints of the peduncle. The 

 peduncle of the uropods is distinguished fr(>in that of longistyUs 

 by being scarcely twice as long as bi'oad and on the outer side at 

 the middle becoming suddenly narrower. This recalls th^ corre- 

 sponding structure in Ligidium hypnorum. Unluckily Dana could 

 not describe the rami because they were mutilated. He does not 

 describe the mouth-organs either in this species or in longistylis, 

 so that the genus remains obscure, covering two species which are 

 very doubtfully congeneric. Styloniscus gracilis is mentioned by 

 Stimpson in 1857, Budde-Lund in 1885, and Miss Harriet 

 liichardson i)i 1899 ; but they neither quote nor supplement the 

 meagre description given by Dana in the Pr. Ac. Philad. vol. vii. 

 p. 176. 



Sars makes the suggestion (Crustacea of Norway, vol. ii. p. 167) 



that the genus Scyphacdla of S. I. Smith may ])erhaps turn out 



to be identical v^ith NnpIophthaJmns of Scliobl. A distinguishing 



feature of llaj>hij>lil](ahiiiis is. hnwcvei', as the name implies, that 



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