538 REV. T. E. R. STEBBING ON CRUSTACEANS [May 22, 



wholly uncovered, digitiform-arborescenfc branchiae, these being 

 partially covered in the Lophogastridae and EiicopiidaB, wanting in 

 the Mysidae, and not arborescent in Anaspides. 



Gen. EuPHAUSiA Dana. 



1852. EupJiamia, Dana, U.S. Expl. Exp. vol. xiii., Crust, pp. 637, 

 639. 



1863. Euphausia, Claus, Zeitschr. fiir wiss. Zool. vol. xiii, pt. 3, 

 p. 442. 



1876. Euphausia, Claus, Genealog. Grundlage des Crustaceen- 

 Systems, p. 7. 



1883. Euphausia, Sars, Christiania Vidensk.-Selsk. Forh. no. 7, 

 p. 11. 



1885. Euphausia, Sars, ' Challenger ' Schizopoda, Reports, vol. 

 xiii. p. 63. 



1893. Euphausia, Ortmann, Decapoden u. Schizopoden, Plankton- 

 Exp. vol. ii. p. 10. 



This genus is distinguished from others in the same family by 

 having the last two pairs of trunk-legs (that is, the fourth and 

 fifth peraeopods) rudimentary, except in regard to the branchiae, 

 which are strongly developed. 



The beautiful and elaborate figures with which Sars has illust- 

 rated this genus refer to a form which he calls Euphausia pellucida 

 Dana. His reason for choosing the name is that so common a 

 form caunot reasonably be supposed to have escaped the attention 

 of Dana, and that of the four species described by Dana the one 

 named pellucida seems to agree with it best. Against this reason- 

 ing there is much to be urged. Sars speaks of " the specimens 

 examined by Dana;" but Dana's description would rather lead one 

 to suppose that he had only at command a single specimen, of the 

 female sex. A single specimen resulting from a four years' voyage 

 may just as well belong to a rare species as to a common one. 

 Dana's descriptions in some cases are, as Sars observes, anything 

 but satisfactory. They are sometimes inconsistent one with 

 another and with the figures to which they refer. In his account, 

 for example, of E. pellucida he says that the last three joints 

 of the feet are together nearly twice as short as the preceding 

 joint. This is not borne out by his detail-figure even of the " pos- 

 terior thoracic leg," and is still less likely to be true of the preceding 

 feet. It is very far from true of any of the feet in the form 

 described by Sars ; but this is separated from Dana's by other 

 characters. Dana describes each of his species as " brevissime ros- 

 tratus," and it is dilBcult to suppose that he could have overlooked 

 such a difference in the length of the rostrum as exists between 

 the forms named by Sars respectively E. pellucida Dana and 

 E. splendens Dana, the rostrum in the former reaching to the 

 distal end of the eyes, and in the latter " scarcely projecting beyond 

 the ocular segment." The pellucida of Sars is distinguished by 

 the great length of the denticulate basal spine of the second 

 antennae, this spine being short in Dana's detail-figure. In pel- 

 [22] 



