390 BEV. A. M. JfOKMAN AND MB. G. S. BEADY 



of (about fourteen) very minute teeth, the two last of which 

 however are considerably larger than those which precede them ; 

 supero-posteal angle distinct, but not produced, nearly a right 

 angle ; claws very long and slender, scarcely curved, but some- 

 what fiexuous, furnished near the base with two spines situated 

 close together, of which that nearest the base is much the smaller. 

 Length, Troth of an inch. 



In outline, and in the character of the abdomen, this species 

 approaches very closely to L. truncatus, from which it is distin- 

 guished by the total absence of the armature of the posterior 

 extremity, and of the anterior portion of the ventral margin, as 

 well as by the different character of the surface-sculpture of the 

 carapace. 



We have felt some hesitation as to what name this species 

 ought to bear. It was first named, but not described, in 1858, 

 by Schoedler, as Pleuroxus omatus ; next, in 1861, it was de- 

 scribed by Gr. 0. Sars, under the name of Pleuroxus Icevis ; in the 

 following year Sars changed the name which he had applied to 

 it to Pleuroxus hastatus, and about the same time Schoedler de- 

 scribed it under the title which he had previously given in M.S. 

 The name, omatus, therefore, dates from 1862, as does also that 

 of Sars, hastatus: the "only way out of the wood" appears to 

 be the adoption of the first name of Sars, viz., Pleuroxus Icevis. 

 Confusion almost invariably arises from an author attempting to 

 change a name which he had already given to a species. For 

 the last seventy years it has been a constant bone of contention 

 among carcinologists which of the two names, vetula and sima, 

 given by Muller to the commonest species of Daphnia, should be 

 retained. The majority of writers have used the latter and later- 

 applied name ; the minority have held that an author has no 

 power to change a name once given, and with them the species 

 bears the name D. vetula. G. 0. Sars is one of those who, as we 

 hold rightly, adopts the first-given name of vetula, and in this 

 precisely parallel case we apply the same rule to his own names, 

 and have called the present species Lynceus Icevis. 



"We have not seen the reticulation of the surface as distinctly 

 marked in any of our specimens as it is represented in Schoedler' s 



