258 BULLETIN OF THE 



horn (b) resembles that of the index (a), while the teeth of the distal 

 horn (f) mark it as the analogue of the index. There is no trace of 

 articulation at the base of either horn. 



There are several specimens similar to this in the collection of the 

 Peabody Academy of Science, Salem, and two or three in the collection 

 of the Boston Society of Natural History. 



Plate I. Fig. 3 (right chela). — Dactylus (a) slightly flexed from the 

 ])lane of the index and broken off about an inch from the tip. From 

 the inner side of the dactylus, near the fracture (d), arise two toothed 

 processes (6, c), directed forwards, which repeat in form the lost tip of 

 the dactylus and the tip of the index. A short, blunt process, directed 

 upward and forward, projects from the inner margin of the dactylus, at 

 a point a little beyond the middle. 



Plate I. Fig. 4 (right chela). — Here the dactylus (a), a short distance 

 from its articulation with the hand, is bent at a right angle with its 

 normal trend, and thrown out from the plane of the hand so that it 

 crosses the index when closed. The tip is broken off. From the un- 

 toothed margin of the dactylus, near the proximal end, proceed two pro- 

 cesses (6, c) at an angle of about 45° to one another, the distal one (c) 

 taking the normal direction of the index. Both of these processes are 

 toothed on their opposed margins, but it is noteworthy that the teeth of 

 the two processes are not directed exactly toward each other, but are 

 inclined a little downward, as if by attraction to the teeth of the thumb. 

 It is curious to observe that the toothed margins of the index and 

 thumb are beset with an imcommonly large number of stiff setse, and 

 that this character is repeated in the toothed edges of the monstrous 

 processes 6, c. 



Plate I. Fig. 5 (left chela). — Similar to Fig. 2, but the processes h 

 and c, instead of diverging from one another, cross one another near 

 their tips like the index finger and thumb of the claw when closed. 



Plate I. Fig. 6 (right chela). — In this claw, unlike what we have seen 

 in those before noticed, the prehensile power has not been lost, the dac- 

 tylus closing accurately upon the index. Just beyond the middle of the 

 dactylus springs a simple branch directed forwards at an angle of 45" 

 with the long axis of the dactylus. This branch shows no tendency to 

 form teeth. 



Plate I. Fig. 7 (left chela). Here the dactylus {a) is bent near the 

 middle, at almost a right angle with its normal direction, away from the 

 index, but is thrown very little, if any, from its true plane of motion. 

 It has acquired an abnormal length, and developed two processes from 



