\ 



900 MR. J. Y. JOHNSON ON NEW CRUSTACEANS. [NoV. '29y 



Tlie species is dedicated to Dr. Alphonse Milne-Edwards, of the 



Jardin des Plantes, Paris, the son of the celebrated author of the 



' Histoire Naturelle des Crustacees,' and himself the author of several 



aluable contributions to carcinological science. 



The following dimensions were afforded by the Madeiran specimen, 



which has been added to the collection of the British Museum :— 



inches. 

 Length from tip of rostrum to end of caudal plates . 131 



of rostrum. 2g 



Carapace, length from base of rostrum to middle of 



posterior margin 3^ 



, width near the middle 1 2 



.height - If 



Eyes with their stalks, length f 



Superior antennae, length of peduncle 1^ 



Inferior antennae, length of lamellar palp 1| 



, width I 



Jaw-feet, length of external pair 4 



, length of next pair 2 j 



Legs, length of first pair 2| 



, length of third pair 5 a 



, length of hand and fingers of third pair 1 5 



Abdomen, length to end of caudal segment 6g 



False legs, length of first pair 4 ^ 



. , length of last pair 2| 



Middle caudal segment, length Ig 



PeNvEtjs bocagei, mihi, P. Z. S. 18G3, p. 255. 



I will take this opportunity of stating that the Penceus of the 

 Tagus, described by me under the name of P. bocagei, is identical 

 with the P. longirostris of M. Lucas (Exploration Scientifique de 

 I'Algerie: Crustace'es, p. 46, Atlas, pi. 4. f. 5), as I have ascer- 

 tained by an examination of specimens obtained at Algiers, and by 

 a study of M. Lucas's description. Dr. Camil Heller (Die Crus- 

 taceen der siidlichen Europa) is of opinion that P. longirostris is 

 itself identical with P. membranacevs, Risso, and thinks that Dr. 

 Milne-Edwards, in his ' Histoire Naturelle des Crustacees,' vol. ii. 

 p. 417, has inadvertently attributed to the P. membranaceus of 

 Risso some of the characters of P. siphonocerus, Phihppi (Archiv 

 der Naturgeschichte, 18-40, p. 19, t. 14. f. 3), which has a very short 

 rostrum, whilst the true P. membranaceus has a long one. If Dr. 

 Heller's views are correct (and I have no reason to suppose that they 

 are not), it will be seen that the range of P. membranaceus, Risso 

 (not Milne-Edwards), is not, as has been hitherto believed, limited 

 to the Mediterranean. 



It may be useful to point out how the five known species of Me- 

 diterranean Pencei may be distinguished from one another by means 

 of their rostra. 



