-ECH.] 



CRUSTACEA. 



545 



spinous, with two pairs of simple, ovate 

 appendages. Type D. dawsoni. 

 dawsoni, Salter, 1863, Quar. Jour. Geo. 

 Soc, vol. 19, p. 77, and Acad. Geol., p. 

 207, Coal Meas. 

 Dipterocaris, Clarke, 1883, Am. Jour. Sci. 

 and Arts, 3d ser., vol. 25, p. 121. [Ety. 

 dipteros, two-winged ; karis, shrimp. J 

 Carapace elongate, divided along the 

 major axis into two wings ; greatest 

 width anteriorly ; wings united medi- 

 ally for one-third to one-fifth the length 

 of the carapace; anchylosed, but sep- 

 arated toward the ends. Surface marked 

 concentrically. Type D. pennidsedali. 

 pennidaedali, Clarke, 1883, Am. Jour. Sci. 

 and Arts, 3d ser., vol. 25, p. 122, Che- 

 mung Gr. 

 pescervae, Clarke, 1883, Am. Jour. Sci. 

 and Arts, 3d ser., vol. 25, p. 123, Che- 

 mung Gr. 

 procne, Clarke, 1883, Am. Jour. Sci. and 

 Ans, 3d ser., vol. 25, p. 122, Chemung Gr. 

 Ditiiykocaris, Scouler, 

 1844, Syn. Carb. 

 Foss., Ireland & 

 McCoy, 1855, Brit- 

 ish Pal. Rocks, p. 

 181. [Ety. dithyros, 

 having two valves; 

 VJf/^ ''.% "*W torn, shrimp.) Car- 



1/^""-- - \f apace semioval ; an- 



terior end rounded, 

 sometimes notched; 

 posterior end sub- 

 truncate, with lat- 

 eral angles produced into spines; sur- 

 face with faint imbricating stria*, mar- 

 gins thickened and corrugated, with 

 three longitudinal lidges, one in the 

 middle extending the entire length, the 

 others not reaching the margin ; tail 

 terminating in three tri- 

 angular spines. Type D. 

 scouleri. 

 belli, see Mesothyra belli, 

 carbonaria, Meek & Worthen, 

 1870, Proc. Acad. Nat. Sci. 

 Phil., p. 55, and Geo. Sur. 

 111., vol. 5, p. 618,Coal Meas. 

 neptuni, see Mesothyra nep- 

 tuni. 

 Dolichocephala, Claypole, 1883, 

 Proc. Am. Phil. Soc, p. 238, 

 syn. for Stylonurus. 

 lacoana, syn. for Stylonurus 

 excelsior. 

 Dolichometopus, Angelin, 1852, Paleonto- 

 logia Scandinavica. [Ety. dolichos, 

 long; metope, panel or space between 

 two hollows.] Cephalic shield with tu- 

 mid margin ; eyes large, narrow, lunate ; 

 glabella wider in front, smooth, no lat- 

 eral furrows ; neck furrow-marked ; 

 facial sutures, beginning at the poste- 

 rior margin near the lateral angles, are 

 directed toward the eyes, passing 

 which, they diverge to the anterior 

 margin ; pygidium semicircular, strongly 



Fig. J00L — Ditbyro- 

 c a r i s corbonaria. 

 Telson and stylets. 



convex, margin entire, axis almost 

 semicylindrical, with two or more fur- 

 rows. Type D. suecicus. It is doubt- 

 ful about this being an American 

 genus, as the identifications have been 

 made alone on the Rygidium. 



?convexus, Billings, 1865, Pal. Foss., vol. 

 1, p. 269, Quebec Gr. or Up. Taconic. 



?gibberulus, Billing.-*, 1865, Pal. Foss., 

 vol. 1, p. 269, Quebec Gr. or Up. Taconic. 



?rarus, Billings, 1865, Pal. Foss., vol. 1, p. 

 352, Calciferous Gr. 

 Dolichopterus, Hall, 1859, Pal. N. Y., vol. 

 3, p. 414. [Ety. dolichos, long; pteron, 

 wing.] Cephalic, thoracic, and caudal 

 portions similar to Eurypterus; post- 

 oral plate lyrate or cordiform lyrate; 

 central thoracic appendage from the 

 first thoracic segment, strong, thick, 

 and simple, in its anterior part; ante- 

 rior feet composed of strong, thick 

 joints, with curved terminal spines; 

 natatory organs having the joints elon- 

 gate, the seventh and eighth little 

 dilated, and the terminal palette ex- 

 tremely developed. Type D. macro- 

 chirus. 



macrochirus, Hall, 1859, Pal. N. Y., vol. 

 3, p. 414, Waterlime Gr. 



mansfieldi, Hall, 1877, Trans. Am. Phil. 

 Soc, p. 621, Lower Coal Meas. 

 Echinocaris, Whitfield, 1880, Am. Jour. 

 Sci. and Arts, 3d ser., vol. 19, p. 34. 

 [Ety. echinos, sea urchin ; karis, shrimp.] 

 Carapace bivalve; valves subovate, 

 united dorsally by a straight hinge, 

 anterior, posterior, and basal margins 

 rounded ; surface marked by longitu- 

 dinal ridges or representative nodes or 

 ridges; abdomen naked, composed of 

 several segments and a caudal plate, 

 which is produced into an elongated 



Fig. 1002.— Echinocaris punctata. 



spine, with a lateral movable spine on 

 each side ; posterior margin of the ab- 

 dominal, segments bearing spines. 

 Type E. sublaevis. 



condylepis, Hall, 1888, Pal. N. Y., vol. 7, 

 p. 173, Chemung Gr. 



longicauda, Hall, 1863, (Ceratiocaris lon- 

 gicauda,) 16th Rep. N. Y. St. Mus. Nat, 

 Hist., p. 73, Genesee Slate. 



multinodosa, Whitfield, 1880, Am. Jour. 

 Sci. and Arts, 3d ser., vol. 19, p. 38, Erie 

 shales. 



