Decapod Crustacea of Bermuda, Part II. 61 



five, never more). The telson is strong and has four small dorsal 

 spines usually, nearly in a quadrangle, and two at each distal angle ; 

 the apex is occupied by a median and several pairs of long plumose 

 hairs or setae, often numerous. The uropods are usually broad, 

 rounded distally, the edge bordered with long pinnate hairs with 

 some longer setiform hairs intermingled ; usually there is also a 

 submarginal row of small acute setae or spinules. The outer 

 lamella of the uropods generally bears a distal movable spine at 

 the sutural notch (rarely two) and usually the angle is also spini 

 form. In our figures of these parts the abundant plumose hairs 

 are usually partly or entirely omitted, or only indicated. (See pi. 

 27, fig. iS.) 



Mandibles are deeply forked, of various forms; always having 

 a two-jointed palpus; inner antennae (antennules) are unequally 

 biflagellate ; the outer flagellum is usually bifurcate. Scale of 

 outer antennae is usually well developed, but not very large, some- 

 times abortive ; it is supported by a strong, external, marginal 

 spine, and bordered on the inner edge with long pinnate hairs ; 

 a smaller basal spine (basicerite) is usually present on the outer 

 angle of the second article of the peduncle ; it is sometimes bilobed ; 

 sometimes nearly or quite abortive. 



The two principal genera, Alpheus (of authors) and Synalphcus, 

 are able to make a sharp snapping sound by suddenly closing the 

 dactyl of the large chela. Most other genera lack this power. 

 A dorsal cardiac notch or pit is always present near the posterior 

 edge of the carapace, and it is eminently characteristic of the 

 family. 



The epipods of the first and second maxillipeds are undivided, 

 without pleurobranchiae. Third maxilliped always has an exopod ; 

 the median article of its endopod is always the shortest; third to 

 fifth legs are short, compressed, fifth smallest ; propodite spinulose ; 

 the dactyl is generally either simple or biunguiculate, rarely tri- 

 unguiculate; the fifth pair have an oblique brush of hairs and 

 spines on the propodus. Two retinules are present on the second 

 pleopod of .the male, except in Synalphcus and Automate. 



Third abdominal segment is short, not abruptly bent down. 

 The telson often has a pair of anal tubercles beneath, and corre- 

 sponding cups which serve as a pair of adhesive suckers, to hold 

 the telson and uropods bent in position. Five pleurobranchiae are 

 always present; other branchiae various. 



