336 BULLETIN 12f), UNITED STATES NATIONAL MUSEUM 



The external maxillipeds have the merus at least as wide as the 

 ischium. (Alcock.) 



KEY TO THK AMERICAN GENERA OF THE SUBFAMILY MAJINAE. 



A'. Eyes furnished with orbits, complete or fairly so. 



B'. Orbit formed (1) by a supraocular hood, the postero-external angle of 

 which is often produced as a spine, (2) by a sharp postocular tooth and 

 (3) by a spine intercalated between the two. Basal antennal article 

 broad but not specially produced to form a floor to the orbit; usually 

 armed at both its anterior angles with a strong spine. 

 C. Cardiac lobe not surrounded by a deep trench. 



D'. Carapace broadly ovate-triangular. Basal antennal article very 

 broad, three-spined. Rostral horns each with an accessory 



spine Maiopsis, p. 337. 



D^. Carapace oblong-triangular. Basal antennal article of moderate 



width, two-spined. Rostral horns simple Paramithrax, p. 338. 



C^. Cardiac lobe surrounded by a deep trench except anteriorly. Carapace 



narrow, suboval Temnonotus, p. 340. 



B*. Orbits completely enclosed, often outstanding and tubular, and formed 

 (1) by an arched supraocular hood or semi-tubular horn, (2) by a hol- 

 lowed postocular process and (3) by a remarkable broadening, or by a 

 prolongation, of the anterior part of the basal antennal article; and at 

 the same time affording a complete concealment to the retracted eye. 

 C. Orbits not projecting sideways beyond the general outline of the cara- 

 pace. 

 D'. Carapace oblong-oval, hairy. Legs and movable articles of peduncle 

 of antennae narrow and bordered with thick fringes of long hair. 

 Dactyls of legs very small, subprehensile. Rostral horns long and 



narrow Thersandrus, p. 343. 



D^. Carapace subtriangular. Legs cristate. 



E'. Merus of ambulatory legs with a thin, lamellate, posterior expansion. 

 No preorbital tooth. 

 F'. Carapace very high on median line. Basal article of antennae 



broader than long Hemus, p. 345. 



F^. Carapace not noticeably high on median line, lobulate. Basal 



article of antennae no broader than long Thoe, p. 347. 



E^. Merus without posterior (or inferior) expansion, but cristate above. 



A preorbital tooth present Teleophrys, p. 440. 



C^. Orbits projecting sideways more or less beyond the general outhne of the 

 carapace, and often tubular. 

 D^ A very long, elevated, preocular spine, twice as long as remainder of 

 orbit. Legs filiform; movable article of antennal peduncle more 



slender and cylindrical Picroceroides, p. 353. 



D*. Preocular spine, when present, not remarkably long. 



E'. Carapace suboval, anteriorly broadly truncate. Rostrum minute, 

 advanced slightly, if at all, beyond the orbits, which have a 

 forward aspect. First movable article of antennal peduncle with 



a leaflike outer expansion Pitho, p. 355. 



E^. Carapace when suboval, without a minute rostrum. 



F'. Fronto-orbital width great, about three-fourths of branchial 

 width. Orbits with a sideways aspect. Rostral horns slender, 

 contiguous. Movable articles of antennal peduncle fiUform. 



Leptopisa, p. 375. 

 F^ Fronto-orbital width less than in F,' usually about half, or less 

 than half, of branchial width. 



