300 U.S. NATIONAL MUSEUM BULLETIN 271 



1. Gnathopod 1 simple Alicella 



Gnathopod 1 subchelate 2 



2. Telson entire, inner ramus of uropod 3 vestigial Onesimoides 



Telson cleft, rami of uropod 3 subequal to each other 3 



3. Coxa 2 perfectly rectangular and elongate, partially covering coxa 1, latter 



shortened, subtriangular; inner plates of maxillae 1-2 fully lined with 



setae medially Valettiopsis 



Coxa 2 short, broad, subrounded, scarcely concealing any portion of coxa 1, 

 latter not shorter than coxa 2 and of similar shape; inner plates of maxillae 

 1-2 with mostly terminal setae, medial edges scarcely or not setose. 



Valettia 



KEY E 



Maxilla 1 lacks a palp, but the mouthparts are arranged in a quadrate 

 bundle, gnathopod 1 is not chelate, and the mandibular cutting edge 

 is not toothed. See Key A, Acidostoma in Key B and Prachynella in 

 Key C. 



1. Gnathopod 1 very large, subchelate (fig. 130a), "telson entire" . Pachychelium 

 Gnathopod 1 small, simple, "telson cleft" 2 



2. Antenna 1 : article 2 as long as article 1 Bathyamaryllis 



Antenna 1 : article 2 about half as long as 1 3 



3. Anteroventral corner of coxa 4 acutely produced Vijaya 



Anteroventral corner of coxa 4 rounded Amaryllis 



. KEY F 



These are the cyphocarids, characterized by the distinctly reduced 

 first and second coxae (and occasionally the third), often hidden 

 behind coxa 3 (fig. 122c) but not always, depending on the anterior 

 prolongation of the third coxae (or fourth) . Coxae 3-4 of Metacyclocaris 

 do not fit this key because of their small size but the genus is included 

 for other comparisons. See note of Key A. 



1. Urosomites 2 and 3 coalesced (fig. 122c) Crybelocyphocaris 



Urosomites 2 and 3 separate 2 



2. Mandible lacking palp 3 



Mandible bearing palp 5 



3. Pereopods 4-5 prehensile, article 6 of gnathopod 1 shorter than article 5. 



Mesocyclocaris 

 Pereopods 4-5 not prehensile, articles 5 and 6 of gnathopod 1 subequal . . 4 



4. Telson entire Crybelocephalus 



Telson cleft Metacyphocaris 



5. Uropod 3: inner ramus strongly reduced or absent (fig. I32h) 6 



Uropod 3: rami subequal to each other, well developed 8 



6. Pereopods simple (fig. 117a) Lepidepecreella 



Pereopods prehensile (fig. 131a) " 



7. Telson cleft Mesocyphocaris 



Telson entire Cebocaris 



8. Coxa 2 much larger than 1 and covering it, but coxae 3-4 small, not covering 



anterior coxae Metacyclocaris 



Some of coxae 1-2 or 1-3 covered either by 3 or 4, coxa 4 large 9 



