602 LESTRIDINJ2 JAEGERS. 



The four toes have all the normal number of segments: 2, 3, 4, 5. They present 

 nothing of special interest, beiug of the ordinary size and shape. The hallux, and its 

 accessory metatarsal bone, may, however, be here described. It does not differ appre- 

 ciably throughout the family, except in the genus liissa of Larbuv, for the characters 

 of which, see under the head of the geuus. 



Were it not for analogy, the on melutarscde accessormm might be considered as a pha- 

 langeal rather than metatarsal segment. It is nearly or quite as long as the first true 

 phalangeal bone. It is obliquely llattened, and somewhat twisted upon itself, tapering 

 to a thin, rather acute, apex. Its distal extremity is broadened and oval, bearing a 

 slightly convex articulating surface, which is coaptated with that of the first phalanx. 

 There is no eminence or depression of any consequence for its attachuieut with the 

 metatarsus ; it is oidy loosely connected by ligaments, and enjoys all the freedom of 

 motion which the hallux itself possess. Its essentially metata/sal character is nev- 

 ertheless demonstrated by its irregular and i^eculiar shape ; by the formation of its two 

 extremities ; and by the want of a proper articulation (capsulated and with a synovial 

 membrane) with the metatarsus. 



This bone in the Lcstridina' differs from that of the other subfamilies in being shorter, 

 stouter, with a broader metatarsal extremity, and having a constrictiou about its 

 middle. 



The proximal phalangeal segment is a very short, stout, straight bone, irregularly 

 cylindrical, with slightly enlarged extremities. These have subcircular articulating 

 facets, the proximal concave, the distal convex. The distal segment is merely a mi- 

 nute, irregularly shaped, osseous nodule, 8uj)portiug the claw. 



SuhfamiJy Lestridin^. 



DiAG. Larid^ rostro cerd instructo, rectricibits inediis elongatis, unguilnis vaUdissimis. 



CiT. Tip of the upper mandible overhanging that of the lower. Covering of upper 

 mandible not continuous, the basal half being furnished with a corneous cere, beneath 

 the edges of which the nostrils open. Culmen at first about straight, then rapidly con- 

 vex. Connnissure slightly sinuate, declinato-couvex on the termiual portion. Gouys 

 short, aboiit straight. Rami widely divaricating, their outline about straight. Erai- 

 nentia symphysis well marked. Nostrils lateral, pervious, somewhat club-shaped, being 

 widest at their distal extremity. Wings long, strong, pointed ; the primaries broad 

 and rigid, more or less rounded at the tips. Tail square, or nearly so, the central feath- 

 ers projecting to a greater or less distance beyond the others ; either rounded at their 

 lijjs, or attenuated and filiform. Legs decidedly ambulatorial, placed well forward, 

 supjjortiug the body in a horizontal posture. Tibia; denuded of feathers on tho lower 

 third. Tarsi rather stout, anteriorly transversely reticulated, posteriorly and laterally 

 reticulated, the plates more or less elevated and acutely pointed. Proportions of toes, 

 and their segments, as in other Larida: Webs broad and full, their margins rounded, 

 not excised. Claws large, strong, curved and acute. Of moderate and large size. The 

 bodj' full, the general organization strong and powerful. The changes of plumage in 

 most of the species, with age and season, very great. 



The anatomical characters of this subfamily are fully given under one of its most 

 common and typical species, the Stercorarim i)omatorhinus. 



§. Analytical tahle of the suhgenera and species of Xorth American Lestridince. 



I. Staturamaximus, et forma, robustissimus; pedibirs et rostro validis ; 

 tarso medio digito cum nugue breviore ; cauda brevi, rectricibus 

 mediis latis, vix ultra ca^teras porrectis Buphagus. 



a. Rostri longit. 2.00 poll, et ultra ; altitudo 0.75 ; ab oris angulo 



ad apicem 3.00 B. skua. 



II. Statura minores, et forma graciliores ; pedibus et rostro gracili- 

 oribus ; tarso medio digito cum ungue non breviore ; cauda elon- 

 gata, rectricibus mediis valde ultra c;eteras porrectis Stercorarius, 



a. Tarsis postice asperrimis ; rectricibus mediis latis in apices 



i^xsas, flexibilibus, cajteris 4 pollices longioribus S. pomatorhinus. 



b. Tarsis postici- subasperis ; rectricibus mediis acuminatis, ri- 



gidis, cajteris 4 pollices longioribus S. }}arasiiicu8, 



c. Tarsis postice subasperis ; rectricibus mediis lougissimis, 



flexibilibus, citteris 8 ad 10 pollices longioribus iS. iuffoni. 



