122 PATTEN AND REDENBAUGH. [Vol. XVI. 



median, and anterior sides of the propodite, is inserted upon the 

 arthroidal membrane between the bases of the whorl of spatu- 

 late organs upon the distal extremity of the propodite, and acts 

 as a flexor for them all, as well as for the slender dactylopodite 

 {6-dac.). A smaller muscle arising from the outer side of the 

 propodite, and inserted upon the outer proximal margin of the 

 dactylopodite, acts as the extensor of this joint, and also of 

 the spatulate organs. The inner proximal margin of the dac- 

 tylopodite extends like a spur toward the bases of the spatu- 

 late organs, and upon the contraction of the extensor muscle 

 acts as a lever and lifts up the arthroidal membrane in the 

 middle of the whorl of spatulate organs. This action tips 

 them outward. 



At the distal end of the longer joint are two smaller append- 

 ages opposed to each other like a chela, and opened and closed 

 by small flexor {fJ) and extensor {eJ) muscles. 



In the sixth appendage, as in the second, the inner mandible 

 with its flexor muscle is absent. 



The Muscles of the Chilaria (Text-fig. 4). — These muscles 

 are comparable with those of the abdominal rather than with 

 those of the thoracic appendages. A muscle (Text-fig. 4, Pis. 

 VII and VIII, Figs. 2 and 3, 7") arises from the roof of 

 the occipital ring, and is inserted by two slips to the posterior 

 and anterior sides of the chilarium. This muscle draws the 

 appendage forward. A few transverse strands of muscle 

 fibers (7"^) are attached to the posterior margins of the bases 

 of the two chilaria, and draw the two appendages toward 

 the median line. A muscle (7^) arises on the neural side 

 of the posterior process of the endocranium, and is inserted 

 upon the inner margin of the base of the chilarium. 



Another small muscle (7"") arises on the inner side of the 

 capsuliginous bar, and is inserted upon the base of the chilarium, 

 close to the insertion of the last-described muscle. These two 

 muscles aid in drawing the appendage backward and toward the 

 median line. Still another small muscle (7^) arises from the 

 posterior border of the endocranium, outside of the capsuligi- 

 nous bar, and is inserted upon the outer margin of the base of 

 the chilarium. A long muscle (7/) arises from the haemal side 



