CRUSTACEA OF ALABAMA. 35 



ferentiated, and Daphnia one of the more highly differentiated genera. The relation be- 

 tween the genera may be gathered from the accompanying key. 



I. Head with a beak, but with rather short antennules 



* Shell angled or spined above the middle of the posterior margin. 

 f antennules small, immovable, without lateral process. 



ft Antennules movable, with a lanceolate lateral process. 



** Shell salient, or spined at the lower posterior angle. 



II. Head without a beak, antennules movable. 



* Abdomen with dorsal processess to retain the eggs. 

 f Shell oval, with hexagonal markings. 



ft Shell quadrangular, indistinctly marked. 



** Abdomen without dorsal processes. 



Genus Moinodaphnia, gen. nov. 



r . Daphnia. 



2 . Simocephalus. 



3. Scapholcberis. 



4. Ccriodaphnia. 

 (Gen. nov.) 5. Moinodaphnia. 



6. Moina. 



Head strongly arched above, angled in front, with almost a beak behind, antennules 

 long, movable, as in Moina, antennae with a long, unjointed spine on the apical joint of 

 four-jointed ramus, body quadrate, merely slightly angled above ; post-abdomen long, 

 with the bifid spines characteristic for Moina, above provided with two evident processes 

 for the occlusion of the brood sac. 



Moinodaphnia alabamensis, s P- »■ 



(Plate III, Figs. 13-16.) 



This remarkable species is worthy of special attention in as much as it not only fur- 

 nishes a missing link in this large family, but forms a tie with the fauna of the southern 

 hemisphere. In Moina macleayii of King, from Australia, we have a closely allied form 

 which must be separated from Moina and included in the present genus. Our species, 

 it can hardly be doubted, is a waif from the fauna of the far South, emphasizing the sug- 

 gestions elsewhere observed of the transitional nature of the Alabama carcinological fauna. 



In size this species agrees with the common Moina, being about 1.68 mm. long. 

 The head is produced in front of the rather large eye, fornix somewhat developed, mac- 

 ula with pigment evident, beak considerably developed, antennule long, with a small fila- 

 ment above the middle in front and four feathery apical setae, antennae long, apical joints 

 of both rami with a long, unjointed spine, that of the four-jointed ramus nearly as long 

 as the setae, seta of basal joint of other ramus elongate, labrum large. The post-abdo- 

 men is long, but is normally enclosed within the valves, terminal claw weakly spinulous, 

 post-abdominal spines twelve, lower one bifid. Post-abdomen above with a strong, 



