no. ir,47. FOSSIL GRABS FROM CALIFORNIA -RATHBUN. ?,47 



In the reduction of the last pair of legs, Archceopus shows an affin- 

 ity to the deep-sea Ocypodan genus Retroplwna Gill = Archcvoplax 

 Alcock and Anderson'' (not Stimpson) = Ptenoplax Alcock and An- 

 derson, which has also a large ovoid basal antennular article and 

 similar chelae. 



ARCHCEOPUS ANTENNATUS, new species. 



Plato XLVII, fii-'s. 4-7: Plate XLVIII; Plate XLIX, fl.cs. 2-4. 



Type.— Cat. No. 310G9, U.S.N.M. One adult female, type; one 

 immature female, cotype; one male, cotype. Locality 27, Santa Cruz 

 Quadrangle. 



Found in a soft blue grey sandstone of Chico, upper Cretaceous, 

 ago at Bolsa Point one mile north of Pigeon Point, San Mateo 

 County, California. 



Carapace about If times as broad as long, antero-lateral margins 

 straight and anteriorly converging, postero-lateral margins very con- 

 vex, curving into the bilobed posterior margin. 



Surface uneven ; a transverse ridge across cardiac and branchial 

 regions; cervical suture well marked, its anterior portion straight and 

 oblique; the depressions in the center of the carapace form a broad H. 

 A groove parallel to the posterior margin defines the intestinal region. 

 Surface punctate. A few irregular bands of small well-separated 

 granules are distinguishable on the more elevated portions. A coni- 

 cal tubercle crowns the hepatic region: five conical tubercles, irregu- 

 lar in size and position, are ranged on the antero-lateral margin, one 

 is hepatic, the others branchial: of the latter the anterior is the larg- 

 est and most elevated, the next two are small, the last is considerably 

 larger. 



Anterior margin sinuous. Front or rostrum slender, acuminate, 

 obliquely inclined, extending forward to a point opposite the outer 

 angles of the orbit. Each orbit occupies about one-fourth of the 

 anterior border of the carapace and is deep and well defined (Plate 

 XLVII, fig. 4) ; its highest part (at its middle) nearly as great as its 

 transverse width: upper margin with a triangular tooth or spine near 

 the inner angle (Plate XLVIII, fig. 1), and a more prominent tooth 

 at the outer angle (Plate XLVII, fig. 6), which forms also the antero- 

 lateral angle of the carapace; lower margin also marked at its inner 

 end with a tooth or spine (Plate XLVIII. fig. 2) which is nearer the 

 median line of the crab than that of the upper border. On either side 

 of the rostriform point of the front (which may, however, be a suit- 

 frontal prolongation of the true rostrum), there is a largo, swollen 



"Amor. Nat.. XXVIII. 1894, p. 1044. 



''Jour. Asiat. Soc. Bengal, LXIII, Pt. 2. 1894, p. ISO. 



c Illus. Zool. Investigator, Crust., Pt. '.'>, 1895, explanation of pi. xv. 



