420 Mr. A. O. Walker on Pherusa fucicola {Leach). 



specimens in that collection which are labelled Pherusa fuci- 

 cola, Leach, as it is possible to do without dissection. There 

 are three specimens in spirit labelled P. fucicola, Leach, in 

 Spence Bate's writing. These are evidently the species 

 described in the Brit. Mus. Cat. p. 145, as above mentioned, 

 and differ entirely from the same species as described by Bate 

 and Westwood in the ' Brit. Sessile-eyed Crust.' In the only 

 specimen in which the antennas are perfect the lower are con- 

 siderably longer than the upper, though described in the 

 Catalogue as " scarcely as long as the upper." This is not, 

 however, of much importance, as it depends on the length of 

 the flagellum, which varies much with age and sex in many 

 species. 



There are also three dried specimens marked Pherusa fuci- 

 cola, Leach. These are believed to be Leach's original type 

 specimens. They are described in the ' Catalogue of the 

 Crustacea in the British Museum' by Adam White (1847) 

 as being from Col. Montagu's collection. 



This, as will be seen, is a matter of great importance. An 

 examination of these specimens (which are undoubtedly those 

 from which Bate and Westwood described their P. fucicola) 

 reveals the following facts : — 



1. That Leach was in error when he stated that there was 

 no secondary appendage to the upper antennas (" seta nulla ad 

 articuli quarti basin ") and that the same mistake was made 

 by Bate and Westwood. 



There is such an appendage, but, being very slender and 

 lying close along the flagellum, it is easily overlooked. 



2. That Bate and Westwood were in error in describing 

 the " posterior pair of pleopoda " (uropoda) as " having the 

 rami equal." On the contrary, one of the rami is reduced to 

 a mere scale on the upperside of the other branch. It is 

 this that forms the distal portion of the apparent double 

 telson figured by these authors. 



3. That the same authors have transposed the gnathopods 

 — the one marked " i" is the first and that marked " h " is 

 the second. 



The consequences of these errors are far-reaching, for, on 

 comparison with the Gammarella Normanni of the same 

 authors (Brit. Sessile-eyed Crust, p. 333), it becomes evident 

 that this is the same species. But Stebbing has shown (Ann. 

 & Mag. Nat. Hist., July 1874) that G. Normanni is the 

 female of G. brevicaudata, M.-Edw., which has the second 

 gnathopods furnished with a very large ovate hand ! And 

 here I may say that the Brit. Mus. type specimens agree with 

 Bate and Westwood's and Stebbing's descriptions of Gamma- 



