454 U.S. NATIONAL MUSEUM BULLETIN 271 



Type-species: A. dentata Chevreux, 1912a; 1912b (designated by 

 Chevreiix, 1912a). 



Species: 2, antarctic to N.W. Pacific, littoral to hadal. 



Stilipes Holmes 



Stilipes Holmes, 1908. 



Cacao K. H. Barnard, 1931; 1932. 



Type-species: .S. dislincta Holmes, 1908 (original designation). See 

 Shoemaker, 1964. 



Species: 3, N.E. Pacific, antiboreal, littoral to bathyal. 



Synopiidae, revised 



[including Tironidae] 

 Figures 165-167 



Diagnosis. — Head massive,* and often galeate, produced into a 

 downturned or deflexed rostrum; gnathopods feeble, scarcely sub- 

 chelate, often simple; telson elongate (rarely short), but always as 

 long as peduncle of uropod 1 ; eyes when present coalesced. See 

 Astyridae, Vitjazianidae, Argissidae, Hyperiopsidae, Oedicerotidae. 



Description. — The characters of this family are so subtle that 

 they are practically indefinable, yet taxonomists have little trouble 

 in recognizing a synopiid. An inclusive diagnosis has to be inter- 

 spersed with the words "most species" since there are so many excep- 

 tions to any pair of character alternatives, yet the majority of species 

 shares anyone of the following characters and all species share the 

 majority of them. 



Antenna 1 ^^'ith multiarticulate accessory flagellum (except Jeddo); 

 base of primary flagellum conjoint in male; eyes when present coal- 

 esced dorsally; mandible with poorly developed, slender palp (except 

 Synojna), molar well developed, often extraordinarily large, smooth 

 and dominating mandible, article 3 usually shortened considerably 

 (except in Bruzeliopsis) ; outer lobes of lower lip frequently notched; 

 mouthparts otherwise like basic gammaridean; coxa 4 never much 

 larger than coxa 3; coxae long (as contrasted with Pardaliscidae) ; uro- 

 pods 1-2 with outer ramus shortened; telson cleft (except in Bruzelia, 

 Bruzeliojjsis, and some Synopia), elongate (except Synopia), as long 

 as peduncle of uropod 1; head massive, produced into a deflexed or 



*As tall as or taller than long (length from posterior margin of head to anterior 

 margin of lateral lobe), head (except Tiron) as long as pereonites 1-3 combined. 



