PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



ual often larger than the stylocerite, the internal often wanting; external 



maxillipeds cylindrical in form, very spinous distally ; first segment of the 



carpus of the second pair approximately equal to the sum of the remaining 



segments; following feet flat in the sagittal plane; ventral hook of the 



dactyl as large as the dorsal ; posterior border of the telson almost straight. 



b\ Dactyls of the third, fourth, and fifth feet with two unequal hooks, the 



ventral always stronger (ui) to three times greater), often accompanied 



by a third prominence obtuse or spinous; meropodites often spinous; 



frontal spines always longer than wide at the base Neomebis group. 



h". Dactyls with two hooks approximately equal in width at the base; me- 

 roi)odites smooth. 

 c\ Dactyls long and slender; hooks directed with the axis of the dactyl, 

 little curved, the dorsal longer; scale of the scaphocerite always pres- 

 ent; lateral spine of the basicerite slender; stylocerite longer than 

 the basal article of the antennulte. 

 d\ Frontal teeth always longer than wide and spinous; rostrum armed 

 with a vertical prolongation which embraces the ocellary beak. 



Paulsoni group. 

 d^. Frontal teeth squarish, at most with concave margins; rostrum with- 

 out inferior vertical prolongation Brevicarpus group. 



c". Dactyls short ; hooks strongly curved, the ventral directed normal to the 



lower border of the dactyl; scale of the scaphocerite ordinarily much 



reduced, often wanting; lateral spine of the basicerite always longer 



than the basal article of the anteunulae, thick ; stylocerite short. 



d\ Small claw with a brush of thick and crowded long hairs normal to 



the dactyl ; stylocerite at most equal to the basal article of the 



autennule; carpus of the small cheliped longer than wide. 



L^viMANus group. 

 d". Small claw without a brush of hairs; stylocerite not reaching the mid- 

 dle of the median article of the antennule ; antennal scale narrow, 

 not reaching beyond tlie extremity of the same article; carpus of 

 the small cheliped short Biunguiculatus group. 



The CoMATTjLARuiM gfoup is cliU'erentiated from the other groups 

 by some very marked characters, which are ahiiost all characters 

 found in the Hippolytida? and therefore suggest a less strong resem- 

 blance to the " Reptantia ;" as frequently happens, there are added 

 to these primitive characters others which show, on the contrary, an 

 adaptation carried very far; for instance, the strongly curved hooks 

 and the movable finger of the small chela surpassing the fixed finger ; 

 these characters are especially marked in S. eomafuIaru>7i, and are 

 explained by its commensalism with the Comatulida, being implements 

 of attachment for the Sijnalpheus. 



This group of very beautiful species appears not to occur on the 

 American coast; the steamer Albatross, of the U. S. Bureau of Fish- 

 eries, has collected a new species of it at the Gilbert Islands, the more 

 remarkable because it possesses only a few of the unusual characters 

 of the group: The spines of the basicerite are equal and short, the 

 first segment of the carpus of the second pair very long, and the fol- 

 lowing feet cylindrical. On the other hand, the antennules are equal 

 to the antennae, the rostrum is scarcely more prominent than the 



