ART. 18 SYNOPSIS OF CALANOID CRUSTACEA — MAESH 33 



as long as the two segments of the exopod; on its inner border, 

 near the base, is an acute spine. The first segment of the basipod 

 of the left foot has four slender acute spines on its inner border. 

 The second segment of the basipod has short spines along its inner 

 border. The first segment of the exopod is short, with an acute 

 spine at its outer distal border. The second segment of the exopod 

 is about twice the length of the first, and is pointed at the end 

 where there are three acute spines. 



Length, 1.2 mm. 



Occurrence. — It has been found in Narragansett Bay, Charlestown 

 Pond at Woods Hole, and in Chesapeake Bay. Willey has reported 

 it in Miramichi Estuary and Minas Basin. It occurs in salt and 

 brackish water. 



PSEUDODIAPTOMUS CRISTOBALENSIS Marsh 



Tlate 16, FiGUBE 7 ; Plate 17, Figxjbes 1-3 

 Pscudodiaptomus oristohalensis Marsh, 1913, pp. 6-8, pi. 2, figs. 1-3. 



The female of this species is unknown. 



The head and the first thoracic segment are coalescent. The last 

 thoracic segment is terminated on each side with a somewhat promi- 

 nent spine (pi. 17, fig. 1). The first three abdominal segments 

 (pi. 17, fig. 2) have spines on the distal borders. The first antennae 

 are composed of 22 segments and about equal in length the cephalo- 

 thorax. The exopods of the second antennae (pi. 17, fig. 3) show 

 clearly only two segments in the central portion. In the fifth feet 

 (pi. 16, fig. 7) the right foot has no endopod. The hook of the 

 right exopod is stout and about equal in length to the second seg- 

 ment. The left foot has a spatulate endopod, which is about twice 

 as long as the first segment of the exopod. The second segment 

 of the exopod is truncate at its distal end, which is armed with 

 minute setae, has a sj)ine about midway of the outer margin, and a 

 minute spine opposite on the inner margin. There is a stout spine 

 on the inner margin at about three-fourths its length and another 

 at the inner distal angle. 



Length, 0.1 mm. 



Occurrence. — Found in the old French canal on the Atlantic side 

 of the Isthmus of Panama. 



PSEUDODIAPTOMUS CULEBRENSIS Marsh 



Plate 17, Figtjees 4-6 ; Plate 18, Figubes 1-3 

 Pseudodiaptomus culebrensis Maesh, 1913, pp. 4r-6, pi. 1, figs. 1-7. 



Fe^nale.— The head (pi. 18, fig. 1) is broadly rounded; the dorsal 

 surface of the last two segments of the thorax is armed with hairs. 



Iu5089— 33 3 



