PODOPHTHALMIA. 



67 



preceding joint, and in Squilla this claw is armed with strong teeth or spines, which 

 are wanting in Gonodactylus, which is represented by a single species, G. chiragra, 

 in the warmer waters of the. Southern States, as well as other parts of the world. 



Order V. — CUMACEA. 



But little popular interest attaches itself to this order, which is represented by only 

 a few small species. Their exact position is a matter of doubt, though their embry- 

 ology shows them, as pointed out by Dohrn, to be intermediate between the Podoph- 

 thalmia and Edriophthalmia. The carapax covers only the first six cephalothoracic 

 rings, and is followed by twelve segments, mostly without appendages. The telson is 

 pointed, but does not extend as far as the appendages of the preceding segment. The 

 anterior cephalothoracic appen- 

 dages (excepting the mandi- 

 bles, which are without palps) 

 are two-branched, but in the 

 three posterior pairs the exop- 

 odites are wanting. The ab- 



-, . , -, 1 , J S'IG. 84. — Diastylis quadrispinoaa, enlarged. 



dommal appendages are better 



developed in the males than in the females, and in tl^e early days of science this differ- 

 ence between the sexes led to the establishment of genera which had no real founda- 

 tion. The organ of vision consists of a single (or two closely approximated) sessile 

 eye in the median line on the front of the body. The respiratory organs consist of 

 branchial plates attached to the first thoracic appendage. 



Besides the differences already alluded to, the sexes may be further distinguished 

 by the antennas ; these in the females are smaller than the antennulse, while in the tnales 

 they are very long. In the females plates arising from three of the thoracic segments 

 form a brood-pouch similar to that which has already been described in the opossum 

 shrimps. In this pouch the eggs undergo their development, hatching in nearly the 

 adult condition. In the flexure of the body, and in the possession of a " dorsal organ " 

 (a structure'of unknown functions), the early embryos show a decided approach to the 

 Edriophthalmia, but later in life they more nearly resemble the Decapods. 



Several species are common on the Eastern shores of the United States, frequent- 

 ing muddy bottoms. They creep about, using the end of the tail to push themselves 

 . forward ; or, folding the tail over the back, they swim with great facility. Their colors 

 are usually dull, though they are occasionally ornamented with more marked tints. 



J. S. KiNGSLEY. 



Fia. 85. — Side Tiew of Alima stage of SqvAlla empusa, enli 



