362 CALIFORNIA ACADEMY OF SCIENCES. 



PSEUDONISCUS Nieszk., 1859; Archiv Nat. Liv-, Esth- u. Kurl., vol. 1, p. 

 381. Silurian. 



BUNODELLA Matt., 1888; Trans. Eoy. Soc. Canada, vol. 6, p. 56. 



Silurian. 

 LIMULID.E. 



BELINURUS Koenig, 1825; Icones Foss., Sectiles, pi. 18, fig. 230. 



Carboniferous. 

 PRESTWICHIA H. W., 1887; Quart. Jour. Geol. Soc. London, vol. 23, p. 32. 



Carboniferous. 



LIMULUS Miiller, 1785; Entomostraca, etc., p. 124. (Triassic.} 



PROTOLIMULUS Pack., 1886; Mem. Natl. Acad. Sci., vol. 3, p. 150. 



Carboniferous. 

 NEOLIMULUS H. W., 1868; Geol Mag., vol. 5, p. 1. Silurian. 



PHYLLOCAEIDA. 

 I. CARAPACE UNIVALVE. 

 I. Flat or slightly convex shield. 



1. Neither sutured nor ridged along the back. Notched in front. 



A. Posterior border entire. 



DISCINOCARIS. H. W., 1866; Quart. Jour. Soc. Geol. London, vol. 22, p. 504. 

 Kound shield, angular notch. Middle and Upper Silurian (Murch.) 

 Aspidocaris Eeuss, 1867. Triassic. 



SPATHIOCARIS Clarke, 1882; Am. Jour. Sci., 3d series, vol. 23, p. 477. An- 

 gular notch. Devonian. 



PHOLADOCARIS H. W., 1882; Geol. Mag. decade 3, vol. 9, p. 388. Sinuous 

 notch. Devonian. 



LISGOCARLS Clarke, 1882; Am. Jour. Sci., 3d series, vol. 23, p. 478. 

 Oblong notch. Devonian. 



ELLIPSOCARIS H. W., 1882; Geol. Mag., decade 3, vol. 9, p. 444. Bounded 

 notch. Devonian. 



B. Posterior border slightly notched. 



CARDIOCARIS H. W., 1882; Geol. Mag., decade 3, vol. 9, p. 386. 



C. Posterior border deeply notched. Devonian. 

 PTEROCARIS Barr., 1872; Syst. Sil. Boheme, vol. 1, suppl., p. 464. Both 



notches angular. Lower Silurian (Murch.) 

 DIPTEROCARIS Clarke, 1883; Am. Jour. Sci., 3d series, vol. 23, p. 121. Both 



notches angular. Cambrian. Devonian. 



CRESCENTILLA Barr., 1872; Syst. Sil. Boheme, vol 1, suppl., p. 507. Both 



notches angular. Lower Silurian (Murch.) 



2. Ridged along the back. 



DITHYOCARIS (Scouler) Portl.; Geol. Eep. Londonderry, etc., 1843, p. 313. 



Eidges sometimes prickly. Devonian and Carboniferous. 



EACHURA Scudder, 1878. Only telson known. Carboniferous. 



