376 U.S. NATIONAL MUSEUM BULLErriN 271 



The Synopiidae and Pardaliscidae usually have a well-developed 

 accessory flagellum in contrast to its absence in oedicerotids. 



The Isaeidae (=:Photidae) differ from Oedicerotidae in their 

 glandular pereopods, fleshy telson, and tube-dwelling habits but some 

 Oedicerotidae, lacking rostra, are morphologically similar to photids 

 and differ from them by disparate shortening of pereopods 3-4 in 

 relation to pereopod 5. 



Oedicerotids need extensive generic revision. Ocular shapes are 

 useful for those genera having oculate type-species but deep-sea 

 species lacking eyes often are difficult to classify. If eyes were to be 

 ignored various genera might be combined, such as Oediceropsis and 

 Paroediceroides (but note that the type-species of Oediceropsis has 

 a swollen article 1 of antenna 1); Paroediceroides might he included 

 with Oediceroides except for its acutely produced coxa 4 (a feature 

 which is present or absent in species of other genera) ; Paraperioculodes 

 might be congeneric with Oediceroides and Paroediceroides as coxa 4 

 is not specifically described, or with Oediceropsis as antenna 2 article 

 1 is not described; Oediceroides brevirostris may belong with Paraperi- 

 oculodes (fide Euffo, 1949); Oediceropsis proxima may belong with 

 Paroediceroides. Numerous other examples could be cited. 



Metoediceros Schellenberg (1931) lacks a mandibular palp, uropod 

 3 has a simple peduncle without rami, appears to have lateral, unco- 

 alesced eyes and probably should form the type of a new family with 

 affinities near the Dogielinotidae. 



Key to the Genera of Oedicerotidae ^ 



This key attempts to minimize the characteristics of eyes but several 

 genera cannot remain separate without some reference to eyes, as seen 

 in the later portion of the key. 



1. Gnathopod 2 chelate (fig. 138/b) 2 



Gnathopod 2 subchelate or simple 3 



2. Mandibular molar triturative (fig. 137/c), gnathopod 2 with long lobe on 



article 5 guarding article 6 Pontocrates 



Mandibular molar degraded, not triturative, often bearing articulate spine (s), 

 article 5 of gnathopod 2 not lobate (fig. 137Z) Synchelidium 



3. Primary cutting edge of mandible short, poorly projecting, untoothed 



(fig. 137A;) 4 



Primary cutting edge of mandible strongly projecting, toothed (fig. 137Z) . 8 



4. Gnathopod 2 with posterior lobe of article 5 partially or fully guarding 



article 6 (figs. 13Si,j,l) 6 



Gnathopod 2 with posterior lobe of article 5 projecting at right angles, not 

 guarding article 6 (figs. 13Sd,h,m) 5 



' Oedicerina Stephensen (1931) is not included; many of its features are not described because tlie type is 

 a broken specimen. 



