FAIRY SHRIMP — LYNCH 557 



(lateral side is usually highest) and the transverse diameter is usually 

 greater than the anteroposterior diameter. On the largest bosses 

 the verrucose part may be 450 microns high on the lateral side, and 

 the entire eminence 530 microns high. Length and breadth are 

 usually somewhat greater than the height. Less elevated above 

 the surface, the bosses of the genital segments are large, but less 

 prominent than those of the thorax. Equivalent structures occur on 

 abdominal segments 1 to 6, but are small, scarcely rise above the 

 surface, and are normally distinguishable only by the use of the 

 compound microscope. 



The females of B, campestris also differ from those of B. mackini in 

 the following minor characteristics : (1) The spines on the distal 

 median border of the endopodite of the female B. campestris are of the 

 same type as those of B. mackini, but are relatively longer. In 

 individuals of the same size, those of campestris are twice as long as 

 those of mackini. (2) The antennule is usually from 85 percent to 

 100 percent of the length of the antenna, sometimes slightly longer. 

 In B. mackini it is always longer than the antenna, averaging 185 

 percent as long. (3) In B. campestris 70 percent of the specimens 

 have no connecting cells between the anterior and posterior groups 

 of cement-gland cells, and the remainder have only a few, separated 

 cells. In B. mackini 85 percent of the females have a continuous 

 strand of juxtaposed cells on the dorsal side of the uterus connecting 

 the anterior and posterior masses of cement-gland cells, and the re- 

 mainder have scattered cells. (4) The ovisac is relatively shorter in 

 campestris, where it terminates under abdominal segment 4 in 59 

 percent of the females and never extends posteriorly to segment 5. 

 In B. mackini, the length of the ovisac is more variable but on the 

 average is longer since it terminates under abdominal segment 5 

 in 69 percent and under segment 6 in 11.5 percent of the females. 



Other American species in which the distal article of the antenna 

 of the male is compressed and turned in at the tip can be distinguished 

 from B. campestris by a number of features, of which the following 

 are most easily recognized: 



B. packardi Pearse, 1912: The males have both an apophysis and a 

 large, proximally inclined protuberance on the median side of the 

 proximal article of the antenna. The female has conspicuous conical 

 lobes on the lateral side of the thorax, those of segments 9-11 and the 

 first genital segment being the largest. 



B. lindahli Packard, 1883, revised by Sliantz 1905: The males have 

 no apophysis or other protuberance on the median side of the basal 

 article of the antenna. Full-grown females have lateral conical lobes 

 on thoracic segments 4-11, those of segments 4-7 being the largest. 



B. coloradensis Packard, 1874, revised by Shantz 1905. The male 



