566 



CRUSTACEA. 



[RHA. SHU. 



PIG. 1054. Remo- 

 pleuridesstriatu- 

 lus. a, ft, Hypo- 

 stoma. 



convex, Voval, narrower anteriorly 

 and abruptly bent down over the 

 front ; eyes large, 

 semilunar, reaching 

 the neck segment; 

 rostral suture marked ; 

 free cheeks, small, 

 narrow, subtriangular, 

 and produced poste- 

 riorly in spines ; tho- 

 rax with ten segments, 

 axial lobe very wide, 

 and gradually taper- 

 ing posteriorly; side 

 lobes narrow, pleura> 

 short, falcate, directed 



/\ A backward ; pygidium 



/ 1 1 small and terminating 

 in two short spines. 

 Ill Type R. colbi. 



V affinis, Billings, 1865, 

 j^^u Pal. Foss., vol. 1, p. 

 jfr 325, Quebec Gr. 



canadensis, Billings, 

 1865, Pal. Foss., vol. 

 1, p. 182, Chazy Gr. 

 panderi, Billings, 

 1865, Pal. Foss., vol. 1, p. 293, Que- 

 bec Gr. 

 schlotheimi, Billings, 1865, Pal. Foss., vol. 



1, p. 294, Quebec Gr. 

 striatulus, Walcott, 1875, Cin. Quar. Jour. 



Sci., vol. 2, p. 347, Trenton Gr. 

 Ehabdichinites, Dawson, 1873, Am. Jour. Sci. 

 and Arts, 3d ser., vol. 5, p. 20. A name 

 proposed for certain markings on the 

 rocks which are not the remains of or- 

 ganisms. 



RHACHURA, Scudder, 1878, Proc. Bost. 

 Soc. Nat. Hist., vol. 19, p. 296. [Ety. 

 rachis, ridge; oura, tail.] Type R. 

 venosa. 



venosa, Scudder, 1878, Proc. Bost. 

 Soc. Nat. Hist., vol. 19, p. 296, Coal 

 Meas. 



RHINOCARIS, Clarke, 1888, Pal. N. Y., vol. 7, 

 p. Iviii. [Ety. rhine, file ; karis, shrimp.] 

 Cephalothorax univalyular, laterally 

 appressed; outline as in Ceratiocaris ; 

 anterior extremity produced into a 

 narrow, vertically flattened prora, con- 

 tinuous with substance of the carapace ; 

 axial line with a low ridge ; abdomen 

 composed of not less than four sub- 

 cylindrical somites ; post-abdomen bear- 

 ing three spines, of which the telson is 

 elongate and conical, and the cercopods 

 flattened. Type R. columbina. 

 columbina, Clarke, 1888, Pal. N. Y., vol. 7, 



p. 195, Ham. Gr. 

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



p. 197, Ham. Gr. 



RIBEIRIA, Sharp, 1853, Jour. Geo. Soc., vol. 

 9, p. 157. [Ety. proper name.] Elon- 

 gated, laterally compressed in the form 

 of a Pholas; open at both ends and 

 along the pedal margin, with a thick, 

 transverse, internal plate near the an- 

 terior extremity, behind which is a cor- 



FiG. 1056. Rusich- 

 nitescarbonarius. 



rugated boss for the attachment of a 

 muscle. Type R. pholadiformis. 

 calcifera, Billings, 1865, 

 Pal. Foss., vol. 1, p. 



340, Calciferous Gr. 

 compressa, Whitfield, 



1886, Bull. Am. MUS. FIG . 105 5._Ribei- 

 Nat. Hist. vol. 1, ria calcifera. 

 Birdseye Gr. 

 longiuscula, Billings. Pal. Foss., vol. 1, p. 



341, Calciferous Gr. 

 ventricosa,Whitfield, 1886, Bull. Am. Mus. 



Nat. Hist., vol. 1, p. 344, Birdseye Gr. 



RUSICHNITES, Dawson, 

 1861, Can. Nat. and 

 Geo., vol. 1, p. 363. 

 Ety. rusos, wrinkled ; 

 ichnos, track.] Sup- 

 posed by the author 

 to be the track of a 

 Crustacean, like the 

 Limulus, and consist- 

 ing of two undulated, 

 rounded, contiguous furrows; but the 

 type resembles a fucoid quite as much, 

 if not more, than it does a track, and if 

 related to Rusophycus, which is clearly 

 a fucoid, then it should be referred to 

 the vegetable! kingdom. Type R. 

 acadicus. 



acadicus, Dawson, 1861, Can. Nat. and 

 Geo., vol. 1, p. 363, and Acad. Geol., p. 

 410, Coal Meas. 

 carbonarius, Dawson, 1868, Acad. Geol., 



p. 257, Carboniferous. 



Salteria, Walcott, 1884. The name was 

 preoccupied, and is a synonym for 

 Bailiella. 



Sao, Barrande, 1846, and Syst. Sil. Boh., vol. 

 2. Type Sao hirsute, a primordial form 

 unknown in America. 

 ? lamottensis, Whitfield, 1886, Bull. Am. 

 Mus. Nat. Hist., vol. 1, p. 334, Birds- 

 eye Gr. 



SCHIZODISCUS, Clarke, 1888, Pal. N. Y., vol. 

 7, p. 62. [Ety. schiza, cleft; diskos, 

 quoit.] Carapace valves separable along 

 the hinge; outline circular or ovate, 

 narrow posteriorly ; surface convex or 

 depressed, elevated at the beaks, which 

 are prominent, slightly incurved, and 

 situated anteriorly, hinge-line equaling 

 in length the greatest diameter of the 

 carapace; edge parallel, not gaping, 

 surface concentrically wrinkled. Type 



capsa^larke, 1888, Pal. N. Y., vol. 7, p. 



207, Ham. Gr. 



SHUMARDIA, Billings, 1862, Pal. 

 Foss., vol. 1, p. 92. [Ety. 

 proper name.] Cephalic 

 shield semicircular ; gla- 

 bella convex, subcylin- 

 drical, no eyes, pygidium 

 semielliptical, axis cylin- 

 dro-conical, ribbed, side 

 lobes ribbed, distinguished 

 from Agnostus by the ribs on 

 pygidium. Type S. granulosa. 



