APPENDAGES 



237 



each consisting of a single flagellum formed of short conical joints. 

 The other cephalic ap- 

 pendages increase in 

 size successively. At 

 present the second and 

 third pairs are not 

 satisfactorily known, 

 but appear to have 

 been similar to the 

 fourth and fifth pairs. 

 The second pair is 

 attached at the level 

 of the posterior end 

 of the hypostome. The 

 fourth and fifth pairs 

 have laro-e, triangular 

 coxopodites which 

 served as gnathobases, 

 their inner edges beino- 

 denticulate ; the endo- 

 podites consist of stout 

 joints ; the exopodites 

 are slender, and bear 

 setae which are often 

 arranged in a fan-like 

 manner. 



The first pair of 

 appendages appear to 

 be antennules, whilst 

 the second pair prob- 

 ably represent the an- 

 tennae, the third pair 

 the mandibles, and the 

 fourtli and fifth pairs 

 the maxillae of other 

 Crustacea. The append- 

 ages of the thorax and 

 pygidium do not differ 

 essentially from the two 

 posterior cephalic appendages 



Fig. 142. — Triadhrus becli, Green, x 2^. Utica 

 Slate (Ordovician), near Rome, New York. A, 

 Ventral surface with appendages ; £p, metastome ; 

 Hi/, hypostome. B, second thoracic appendage ; 

 en, endopodite ; e.r, exopodite, x 12. (After 

 Beecher.) 



Those on the anterior part of 



