704 



CRLSTACEA. 



[ACA.— par. 



ently, not ranking higher than species. The central part of the cephalic shield of 

 the Trilobita (treis, three ; lobos, a lobe,) is called the glabella ; the grooves at the 

 sides of it are called axal furrows, the one at the rear the neck furrow ; the fixed 

 cheeks are on each side of the glabella, and separated from the free cheeks by the 

 facial suture, though the facial suture is absent in Trinucleus and some other genera ; 

 the central part of the thorax is the axis, and the side lobes are the pleurae ; the di- 

 viding line is the axal furrow ; the segments of the pygidium are anchylosed. The 

 Xiphosura (xiphos, a sword ; aura, a tail,) have a broad, convex buckler, com- 

 pound, subcentral eyes, and ocelli in front; the mouth has a small labrum and six 

 pairs of appendages; the telson, or terminal segment, is ensiform. 



Acanthotelson magister, Packard, 1886, 

 Mem. Nat. Acad. Sci., vol. 3, p. 127, 

 Carboniferous. 



Acidaspis ortoni, Foerste, 1887, Bull. Deni- 

 son Univ., vol. 2, p. 90, Niagara Gr. 

 peraruiata, Whiteaves, 1891, Can. Rec. 

 Sci., p. 300, Up. Sil. 

 l.( iii.mina, Jones & Holl, 1869, Ann. and 

 Mag. Nat. Hist., Ser. 4, vol. 3, p. L'17. 

 [Ety. aichine, a sharp point.] Valves 

 thick, straight at the hinge, rounded at 

 the ends, convex at the ventral border, 

 and outdrawn at the surface into a 

 broad-based and sharp-pointed hollow 

 cone, which either involves all the sur- 

 face or rises from the postero-dorsal 

 or centro-dorsal region. Type M. cus- 

 pidata. 

 abnormis, Ulrich, 1890, Jour. Cin. 8oc. 

 Nat. Hist., vol. 13, p. 183, Niagara Gr., 

 and A\. marginata, p. 184, from the 

 Ham. Gr. 



Acnostis desideratus, Walcott, 1889, Proc. 

 U. S. Nat. Mus., vol. 12, p. 39, Up. 

 Taconic. 

 latus, see Bollia lata. 



Agraulos redpathi, Walcott, 1890, 10th 

 Ann. Rep. U. S. Geo. Sur., p. 654, Up. 

 Taconic. 



Ampyx americanus, Safford & Vogdes, Proc. 

 Acad. Nat. Sci., Trenton Gr. 



Anomalocaris, Whiteaves, 1892, Can. Rec. 

 Sci., vol. 5, p. 205. [Ety. anomalos, un- 

 like ; karis, shrimp.] A phyllocarid 

 crustacean ; body from 9 to 13 seg- 

 ments, exclusive of the caudal segment, 

 each bearing a pair of slender, nar- 

 rowly elongated and acutely pointed, 

 simple and probably branchial append- 

 ages of the nature of uropods or foot- 

 gills ; posterior terminal segment mar- 

 gined with three pairs of caudal spines, 

 one terminal, the other two lateral. 

 Type A. canadensis, described at the 

 same place from rocks of uncertain age, 

 probably Up. Taconic. 



Aparchites concinnus, Jones, 1858, (Cyther- 

 opsis concinna,) Ann. &Mag. Nat. Hist, 

 Ser. 3, vol. 1, p. 249, Black Riv. Gr. 

 inornatus, Ulrich, 1890, Jour. Cin. Soc. 

 Nat. Hist., vol. 13, p. 182, Up. Held.Gr., 

 and A. oblongus, p. 137, Hud. Riv. Gr. 

 mitis, Jones, 1891, Cont. to Can. Micro- 

 Pal., p. 91, Devonian ; and A. mundu- 



lus and A. tyrrelli, p. 62, from the 

 Chazy Gr. 



Aristozok canadensis, Whitfield, 1890, Ann. 

 N. Y. Acad. Sci., p. 505, Trenton Gr. 



Asaphus has a lip-plate, labrum, or hy- 

 postoma, {hupo, under ; .stoma, mouth ;) 

 that is wide and deeply forked behind. 

 The jointed limbs and branchial fila- 

 ments shown in the illustration of the 

 Oxford specimen in the Jour, of the 

 Cin. Soc. of Nat. Hist., as well as the 

 description of them, are largely imagin- 

 ary, as the specimen does not show the 

 characters. 



Atops reticulata, Walcott, 1890, (Conoc- 

 oryphe reticulata,) 10th Ann. Rep. 

 U. S. Geo. Sur., p. 049, Up. Taconic. 



Avalonia, Walcott, 1890, 10th Ann. Rep. 

 I '. -S. Geo. Sur., p. (140. Type A. man- 

 uelensis, described at the same place 

 from the Up. Taconic. 



Bairdia, McCoy, 1840, Synop. Foss. Ire- 

 land, p. 104. [Ety. proper name.] 

 Carapace varying from a broadly tri- 

 angular to a narrow elongate subtrian- 

 gular form, with extremities more or 

 less acute ; surface smooth and setifer- 

 ous or finely punctate; no central 

 tubercle ; lucid spots well marked ; 

 margins thin and trenchant ; when 

 closed the edges of the right valve lie 

 within those of the left; interior of the 

 marginal borders, except on the dorsal 

 edge, cased with a narrow lamelliform 

 plate, as in Cypris, except that a slight 

 fold or notch is frequently apparent at 

 the angles of the hinge- line; the dorsal 

 edge of the right valve is quite simple, 

 and, in the closed carapace, underlies 

 the dorsal edge of the left valve, which 

 is larger and overlapping ; ventral 

 margin incurved. Type B. curta. 

 anticostiensis, Jones, 1890, Quar. Jour. 

 Geo. Soc. vol. 46, p. 548, Hud. Riv. Gr. 

 cestriensis, Ulrich, 1890, Jour. Cin. Soc. 

 Nat. Hist., vol. 13, p. 210, Kaskaskia 

 Gr. ; and B. leguminoides, p. 197, 

 Ham. Gr. 



Barychilina, Ulrich, 1890, Jour. Cin. Soc. 

 Nat. Hist., vol. 13, p. 198. [Ety. baru», 

 heavy, thick ; cheilos, a lip.] Carapace 

 small, subrhomboidal or ovate ; valves 

 thick, unequal, the right the larger, 

 overlapping the left except in the pos- 



