28 



This specimen is 34 mm. long. That no ovigerous female has 

 yet been captured is not a serious difficulty when it is re- 

 membered that only about thirty-five specimens have been 

 taken in all. 



The Helga has captured ten specimens, including trie types 

 of three new species. Of these one, E. hibernicus, belongs to the 

 division of the genus in which the carapace spines are confijied 

 to a few definite rows as in E. coecus, E. Faxoni, etc. The other 

 two, E. Scharffi and E. Kempi, belong to the group containing 

 E. spinulosus and E. Puritanii, in which the spines are scattered 

 over the whole of the carapace. Perhaps the most interesting 

 of all the specimens taken by the Helga is a very small individual 

 measuring only 7 mm., in which the rostrum has the form of a 

 very long median spine, and only two pairs of thoracic legs are 

 developed. On these, however, and on the second and third 

 maxillipedes there are slender exopodites, so that it is really a 

 young Eryonicus in the My sis stage of development. 



Eryonicus leads a free-swimming life at a considerable distance 

 from the bottom. Most of the Helga specimens were taken by 

 the midwater otter trawl. Others were taken by the beam 

 trawl, but these must have been caught as the latter was being 

 hauled to the surface. The great soundings at some of the 

 stations where specimens have been taken may be very deceptive. 

 Faxon mentions a case where the depth was 1168 fathoms, and 

 where four specimens were caught less than 400 fathoms below 

 the surface. Another of the Albatross specinaens was taken by 

 the trawl where the depth was only 384 fathoms. These facts 

 would seem to show that Eryonicus sometimes comes to within 

 a comparatively short distance of the surface. 



Ten species are known so far and a key for the determination 

 of these is given below. 



Key to species of Eryonicus. 



1. a. Carapace spines almost entirely confined to 



definite rows, . . . . . . . . . . 2 



b. Carapace spines not confined to definite rows but 



also scattered generally over surface, .. 7 



2. a. Two median spines on basal part of telson, 



E. coecus, Sp. Bate. 

 b. One median spine on basal part ol telson, . . . . 3 



3. a. Spines on anterior part of median row of cara- 



pace : rostrum+1, 1, 2, 1, 1, .. .. .. 4 



b. Spines on anterior part of median rows of cara- 

 pace : rostrum^l, 2, 1, 1, .. .. .. 6 



4. a. One spine on outside of basal joint of antennular 



peduncle, . . . . . . . . E. indicus, Alcock. 



b. Two spines on outside of basal joint of antennular 



peduncle, . . . . . . .. .. .. 5 



