390 CRUSTACEA ENTOMOSTRACA. 



many jointed exopodite is the longer of the two rami. Tlie 

 mandibular palp is long and pediform. A respiratory plate is 

 absent from the first maxilla, but present on the second. The 

 halves of the caudal fork are plates bearing spines along their 

 margins, gradually increasing in size towards the terminal 

 extremities of the plates. 



Fam. 1. Cypridinidae. Shell hard, the notch for the antennae 

 situated at or below the middle of the dorso-ventral extent of the shell. 

 First antenna strongly flexed at the articulation between the basal joint 

 and the next. Mandible without a regular masticatory process, this 

 being represented by a small lobed setose plate connected with the basal 

 joint. The large 4-jointed pediform palp bears a small exopodite. The 

 three following appendages are all short and more or less jaw-like and 

 aggregated about the mouth region. The 7th is a many-jointed worm- 

 like structure, the end beset with bristles. Generative orifice single and 

 median. In the male the copulatory organ consists of a pair of structures 

 probably representing a pair of appendages, which arise on either side 

 of the orifice. A heart, two large compound eyes, together with a 

 median eye and rod-like " frontal organ," are present. GypridinaM.. Edw. 

 (Fig. 254), some spp. phosphorescent. Pyrocypris Mull., C rosso pliorns 

 Brady, Gigantocypris Mull., G. Agassizii, obtained by U.S. ss. " Albatross " 

 and since by the " Valdivia," is probably a free-swimming inhabitant of 

 deep water. It is nearly globular in shape, orange in colour, and pro- 

 vided with a pair of mother-of-pearl like plates over the eyes. It attains 

 a length of 23 mm. Philomedes Lilljeb., Pseudophilomedes Miill., Cylin- 

 droleberis Brady, Sarsiella Norm. 



Fam. 2. Haloeypridae. Shell calcified ; the notch for the antennae 

 situated above the middle of the dorso-ventral extent. Numerous uni- 

 cellular glands, opening on the surface, are present along the margins of 

 the shell. Mandible with well-developed masticatory process. 1st max- 

 illae jaw -like ; 5th pair of appendages (mx. 2) with a backwardly directed 

 endopodite, and a respiratory fan on the protopodite ; the sixth are 

 leg-like ; while the seventh are slender, dorsally directed structures bearing 

 a few bristles. The vasa deferentia unite in a duct traversing the penis 

 which lies on the right of the middle line. A heart and " frontal organ " 

 are present, but eyes are absent. Pelagic. Thaumatocypris Miill., 

 Conchoecia Dana, Halocypris Dana, Euconchoecia Miill., Archiconchoecia 

 Miill. 



Fam. 3. Polycopidae. The halves of the shell are round or oval, 

 and the antennary notch shallow or absent. Second antennae with a 

 comparatively narrow basal joint, and approximately equal rami. Mandible 

 with a weak masticatory process. The fourth pair of appendages (mx. 1 ) 

 are not masticatory and bear a well-developed exopodite ; the fifth (which 

 is also the last pair) are short and carry a large respiratory fan. The penis 

 is markedly unsymmetrical. Heart, eyes and frontal organ are absent. 

 Minute Ostracods living at the bottom of the sea. Polycope Sars, Poly- 

 copsis Miill. 



is here a swimming organ and, as in some other Entomostraca, one of the 

 principal organs of locomotion. In the Podocopa these appendages are 

 leg-like. 



