452 APPENDIX TO CRUSTACEA [December, 



Cabinet of the Academy. 



Thorax glabrous, rounded each side, immarginate; 

 eyes sanguineous; anterior feet with the hand Unear, or 

 not gibbous near the base of the thumb above, ciUated 

 on the inferior edge, fingers two thirds the length of the 

 hand, armed with minute teeth; thumb with a prominent, 

 acute tooth near the base, closing between two much 

 shorter distant ones of the finger; carpus with an abbre- 

 viated ciliate line within, third joint ciliate on the inner 

 edge; second pair of feet ciliate beneath the penultimate 

 joint; tarsi unarmed. 



Lengih about one- fourth of an inch. 



1 found a single female of this species in an anoma- 

 lous Byssomia, which in a MSS. account of the shells of 

 North America I have named B, distorta. It imbeds it- 

 self in the large Alcyonium of the southern coast, and be- 

 tween individuals of a species of aggregating Ascidia, 



It is infested by two very distinct kinds of parasites, 

 which I regret not having had an opportunity to examine 

 satisfactorily. One resembled Fascicola with the ocellate 

 points of Planaria. I have named it Fascicola nigra. Body 

 cylindrical, blackish, two ocellate spots near the anterior 

 extremity. It was active, motion undulutory. The other 

 was numerous, attached in two fascicles to the exterior of 

 the thoraX;, and resembled a mi-nute species of Amphitrite. 



3. p. cylindricum^. Body transversely- subcylindrical; 

 anterior feet didactyle, equal; second and third pairs 

 nearly equal, and with punctured tarsi; fourth pair very 

 robust, larger and longer than the anterior ones; posterior 

 pair very small; eyes approximated, orbits ovate grbicu- 

 lar. 



