1885.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 179 



Length of third perseopod lf~'. 3 



Length of uierus 4. 5 



Length of carpus 7.4 



Length of chehi 3. 1 



Breadth of chela 0. 55 



Length of dactyhis 1.4 



Length of fourth peneopod 15. 5 



Length of carpus 3. 8 



Length of propodus 2. 7 



Length of dactylus 1. 5 



Length of tifth perseopod 17. 5 



Length of carpus 4. 5 



Length of propodus 3. 3 



Length of dactylus 1.5 



Length of sixth somite of pereon 8. 



Height of sixth somite of pereon 5.3 



Length of telson 9. 5 



Length of inner lamella of uropod 8. 



Breadth of inner lamella of nropod 1.7 



Length of outer lamella of uropod 8.4 



Breadth of outer lamella of uropod 2. 1 



Hymenopenaeus Smith. 



lu the four species which I have examined both flagella of the anteu- 

 iiuhT3 are slender and at least as long as the carapax, excluding the ros- 

 trum ; the proximal segment of the mandibular palpus is larger and 

 much broader than the distal, which is long and narrow ; the endognath 

 of the first maxilla is short and unsegmen ted; the second guathopod 

 and the first, second, third, and fourth perjeopods have well- developed 

 epipods ; and there is, either side, a i)leurobranchia on the fourteenth 

 somite and two arthrobranchicE on the thirteenth. The branchio-epipo- 

 dal formula is — 



The species examined further agree in having antenual, hepatic, and 

 branchiostegial spines, a fourth spine back of the orbit, and small epi- 

 pods at the bases of all the pera^opods. 



The genus thus differs from both Penccus and Parapenams in the 

 elongated antennular flagella, the form of the mandibular palpus, and 

 in the presence of two arthrobranchise and an epipod on either side of 

 the thirteenth somite ; it agrees with Penccus and differs from Parapen- 

 ceus in having an epipod at the base of the second gnathopod ; and it 

 agrees with Parapencvus and differs from Penccus in having the endqg- 

 nath of the first maxilla short and unsegmented. 



