CALIFORNIA STALK-EYED CRUSTACEA. 13 



The second antennae are usually larger than the 

 first pair and situated behind or external to them. The 

 exopod is represented by a scale, or acicle, attached to 

 the second basal joint, but this structure is often absent, 

 especially in the higher forms. The peduncle usually 

 contains four or five joints and bears an annulated, 

 terminal portion, the flagellum. The first joint contains 

 the opening of the renal organ and is often immovably 

 joined to the carapace. 



The Mandibles. The appendages which function as 

 mandibles are highly modified. The first joint (coxo- 

 podite) is enlarged and modified for the purpose of 

 mastication; this part is called the trunk and its inner 

 edge is generally dentate and often divided into a lower 

 portion, or molar process, and an upper cutting edge. 

 The trunk bears a jointed appendage, or palp, which, 

 in this group, never consists of more than three joints. 



The First and Second Maxillce. The first maxillae are 

 always small and foliaceous. The two basal joints are 

 flattened and produced inward; there is a small endo- 

 podite; the exopodite is usually absent. In the second 

 maxillae the two basal joints are modified much like 

 those of the first pair. There is a small endopodite 

 outside of which is joined a large, flattened appendage 

 {exopodite, scaphognathite) which serves to produce a 

 current of water from the branchial chamber. 



The First Maxillipeds. These are the first thoracic 

 appendages. The two basal joints are flattened and 

 produced, forming the so-called lacmiae, or masticatory 

 ridges. The endopod is small and generally joined to 

 a greater or less extent to the exopod; the latter is well 

 developed and ends in an annulated, terminal portion, 

 or palp. 



