sotne rindescrihed exotic Crustacea. 198 



appendage. Leach and Desmarest consider these as rudimentary- 

 feet, while Latreille looks upon them as branchi?e. There seem no 

 laminae or offsets from them passing into the water, and in delicacy 

 or transparency they are not in the least different from the legs or an- 

 tennae, so that I am inclined to concur in the correctness of the former 

 of these opinions. In the females, between the pairs of appendages, 

 and extending from the anterior inferior extremity of the third seg- 

 ment of the body to the posterior part of the fourth, is to be found 

 a complicated apparatus, which Bosc calls " un ovaire tres volumi- 

 neux lorsque la fecondation est operee." Its essential parts consist 

 of three mobile plates ; one placed anteriorly, and arising by an ar- 

 ticulation from the anterior inferior part of the 3rd joint, is most ex- 

 ternal, and permits the posterior edge of the second plate to project 

 a little from beneath it. The lateral edges of this plate are mem- 

 branous, and continued into the exterior covering of the sides of the 

 3rd and 4th joints, or into little lateral plates occupying the same 

 position, so that a free motion is allowed on the anterior extremity 

 as a centre, towards the belly of the animal, and producing a sliding 

 motion over the other two plates. The second plate is narrower, 

 lies beneath the first, and covers the apical half of the third or pos- 

 terior plate. The third has similar attachments to that first de- 

 scribed from the posterior part of the fourth joint, but has its lateral 

 or superior edge, unlike it, irregularly waved, and extended as far 

 forwards as the vesicular appendage to the 3rd joint. These plates 

 are continually in motion, moving like a hinge on their basal extremi- 

 ties, and sliding over each other against the contiguous plate, as the 

 free edges were made to approximate or recede from the belly of the 

 animal. I succeeded in abstracting a number of young from the 

 cavity, which is perhaps capable of holding a dozen or fifteen. They 

 were not inclosed in a shell, being probably beyond the period re- 

 quired for their sojourn in the egg. Tliey were however rolled up 

 in a little oval ball, the legs and antennaj being all turned in. The 

 fleshy opake part of their body was at a tolerable distance within 

 the hyaline membrane forming the exterior covering of the body, 

 especially in the legs and antennae, where it appeared occupying the 

 centre of the joints like a little heap of dark globules. The joints 

 were proportionably shorter and thicker, but equally numerous as in 

 the adult state. At this period respiration was going on, for I saw 

 the plates forming the ovary in continual motion, the water gliding 

 in and out as the plates were moved with the sliding motion over 

 each other. The edges of the plates are fimbriated to prevent the 

 escape of the minute ova, and at the same time to admit of free pas- 

 sage to the water ; and the blood was distinctly seen penetrating 



