The single North American species of this genus has no near relative in tropical America; indeed, no other species at present known can be said to be strictly congeneric. In all essential details of external structure, and in every respect as to habits and nidification, the type of the genus (_G. cærulea_) is much more like the species of _Cyanospiza_ than those of _Hedymeles_, with which latter it has usually been included. Guiraca cærulea, SWAINSON. BLUE GROSBEAK. _Loxia cærulea_, LINN. Syst. Nat. I, 1766, 306.—WILSON, Am. Orn. III, 1811, 78, pl. xxiv, f. 6.—? WAGLER, Isis, 1831, 525. _Guiraca cærulea_, SWAINSON, Birds Mex. in Phil. Mag. I, 1827, 438.—BAIRD, Birds N. Am. 1858, 499.—COOPER, Orn. Cal. 1, 230. _Fringilla cærulea_, AUD. Orn. Biog. II, 1834, 140; V, 508, pl. cxxii. _Coccoborus cæruleus_, SW. Birds II, 1837, 277.—AUD. Syn. 1839.—IB. Birds Am. III, 1841, 204, pl. cciv.—CABANIS, Mus. Hein. 1851, 152.—FINSCH, Abh. Nat. Brem. 1870, 339 (Mazatlan). _Cyanoloxia cærulea_, BP. Conspectus, 1850, 502. _Goniaphæa cærulea_, BP. _Blue Grosbeak_, PENNANT, Arc. Zoöl. II, 1785, 351. [Illustration: _Guiraca cærulea._] SP. CHAR. Brilliant blue; darker across the middle of the back. Space around base of the bill and lores, with tail-feathers, black. Two bands on the wing across the tips of the middle and secondary coverts, with outer edges of tertiaries, reddish-brown, or perhaps chestnut. Feathers on the posterior portion of the under surface tipped narrowly with grayish-white. Length, 7.25; wing, 3.50; tail, 2.80. _Female_ yellowish-brown above, brownish-yellow beneath; darkest across the breast. Wing-coverts and tertials broadly edged with brownish-yellow. Sometimes a faint trace of blue on the tail. The young resembles the female. HAB. More southern United States from Atlantic to Pacific, south to Costa Rica. Xalapa (SCL. 1859, 365); Oaxaca (SCL. 1859, 378); Cordova (SCL. 1856, 301); Cuba (CAB. J. IV, 9); Vera Paz (SALVIN, Ibis, III, 352); Costa Rica (LAWR. IX, 102); Vera Cruz, winter (SUM. M. B. S. I, 552); Yucatan (LAWR. IX, 200). The species described as _Cyanospiza parellina_ in the Birds of North America, but which so far has not been actually detected north of Mexico, is a miniature _Guiraca_, more related, however, to the _G. concreta_ than to _cærulea_. It is easily distinguished from the latter by more lobed bill, darker back and under parts, absence of rufous wing-bands, and inferior size. Length, 5 inches; wing, 2.50. Males from the Pacific coast region (California, Colima, etc.) have tails considerably longer than eastern specimens, while those from California are of a much lighter and less purplish blue, the difference being much the same as between _Sialia sialis_ and _S. azurea_.