AKT. 17 0]Sr TEERESTEIAL ISOPODS LOHMANDEE 9 



representatives of the genus Deto hitherto known have a subant- 

 arctic range — New Zealand; Australia; St. Pauls Island, Indian 

 Ocean; South Africa; South America. (Chilton, 1914, p. 439.) 

 Even if a close agreement between Deto and DetonelJa is indis- 

 putable, I find it rather difficult, because of the wide geographical 

 difference in their ranges, to suppose a very near phylogenetic 

 affinity between them. The species of the two genera seem to live 

 under rather similar conditions and might be said to supply one 

 another's places respectively in subarctic and subantarctic regions. 

 Therefore it is not impossible that several conformities are con- 

 vergences. Detonella papillicornis is found on the beach in the 

 extreme northern portion of the Pacific Ocean, and Chilton says 

 about the genus Deto (1914, p. 453) : "All the species are strictly 

 seashore inhabitants, probably not extending much above high- 

 water mark or beyond the reach of the spray from the sea. In this 

 respect as well as in many points of structure, they agree with the 

 genera Scyphax and Scyphoniscus, and it is probable that their 

 nearest affinities will be found to be with these two genera. 

 Scyphax differs from Deto in the very large and well-developed eye 

 with its rows of numerous ocelli, and Scyphoniscus in the peculiar 

 structure of the end of the outer lobe of the first maxilla." In 

 regard to these characteristics the genera in question differ also 

 from Detonella. 



The differences between Deto and Detonella will be best illus- 

 trated by the following comparison : 



DETO ^ DETONEILLA. 



Length of adult specimens 11-24 Length of adult specimens 3-4 mm. 

 mm. Eyes of moderate size, with Eyes small, with few ocelli (about 

 numerous ocelli. Antennulae with the 6.) Antennulae with the third joint 

 third joint large, extended, bearing very small, rounded, the apex carry- 

 sensory filaments in two rows distant ing three sensory filaments, the second 

 one from the other, the second joint joint with two articulate setae, at 

 with only one biarticulate plu- least one of which has a pencil bristle, 

 mose seta. The outer lobe of the About half of the teeth of the outer 

 first maxilla with single-tipped teeth, lobe of the first maxilla bifid. The 

 The masticatory lobe of the maxil- masticatory lobe of the maxillipeds 

 lipeds with a very small rudimentary with a well-developed plumose seta, 

 plumose seta; spines seem to be and some strong spines. The exopo- 

 lacking. The exopodites of the pleo- dites of the pleopoda (2-5) only in 

 poda (2-5) in both sexes with v^^ell the male with plumose setae most of 

 developed setae at the postero-lateral which are attached to the inner dor- 

 margins, sal face near the median margin. 



In her monograph Richardson admits only one representative of 

 the family Scyphacidae from North America — that is, Scyphacella 

 arenicola Smith. (Eichardson, 1905, p. 672.) With Scyphacella^ 

 however, of which only the aforesaid species is known, Detonella 



2 Compare Chilton (1914, p. 348) ; and Wahrberg- (1922, p. SO). 

 55225—27—2 



