50 Mr. W. V. Guise on a new species of Alpheus. 



prize, being a Mediterranean species of the greatest rarity in our 

 seas ; but upon comparing it carefully with the descriptions of 

 Milne-Edwards in his e Histoire Naturelle des Crustaces/ I be- 

 came convinced that I had had the good fortune to obtain an 

 entirely new species of Alpheus ; and further investigations have 

 only tended to confirm me in that opinion. 



The genus " Alpheus " is thus characterized by Milne- 

 Edwards: 



Carapace prolonged in form of a hood or vault over the eyes. 



Rostrum small, and sometimes wanting. 



Superior antenna small ; first articulation short, and armed with- 

 out with a plate, generally spiniform ; two following joints cy- 

 lindrical, having two terminal threads, of which the superior 

 is thicker and shorter than the inferior, and presenting traces 

 of a division into two filaments towards the end. 



Inferior antenna inserted without and below the preceding. 



Lamellar palp of moderate size, sometimes small and pointed. 



Mandibles provided with a short, broad, palpiform appendage. 



External pedipalps more or less slender and elongated, termina- 

 tion broad and somewhat foliaceous. 



Two first pairs of legs didactyle, the first pair strong ; the one 

 much larger and more robust than the other. 



Second pair weak and filiform, having the wrist multi-articulate. 



Three last pairs of legs monodactyle and of moderate length. 



This genus, says M. Edwards, appears to belong properly to 

 the seas of warm climates. Some species are found in the 

 Mediterranean ; but the greater part come from the seas of the 

 Antilles or from the Indian Ocean. 



The genus is divided into those which have, and those which 

 have not, a spiniform rostrum. It is further subdivided into those 

 having a spine attached externally to the basal joint of the 

 external antenna, and those not so furnished. 



The example now before us will be found to belong to the 

 second subdivision of the first division, i. e. to those provided 

 with a pointed beak, and not having an external spine at the 

 base of the external antennae. 



Under this head three species are described by M. Edwards as 

 inhabiting the European seas, viz. 



Alpheus ruber, Alpheus Edwardsii, and Alpheus dentipes, which 

 are characterized as follows : 



Alpheus ruber. " Body very slender ; larger hand provided with 

 four longitudinal carinse, two on the upper edge, two on the 



