28 No?Hh American Palseozoic Crustacea. 



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



Lutheri, Clarke, 1882; Am. Jour. Sci., 3d series, vol. 23, p. 478, pi. 1, 

 fig. •'>. Hamilton. 



Mesothyra, Hall & Clarke, 1888 ; Pal. New York, vol. 7, p. 187. 



Diagnosis. — Carapace sub-quadrate in outline, composed of two valves 

 which come into contact at the apices of two broad, sub-triangular 

 extensions, situated on the dorsal line opposite the eye-nodes, forming 

 a short and broad anterior, or rostral cleft, and a long posterior cleft. 

 Rostrum not observed. The posterior dorsal cleft was covered either 

 bv a single elongate plate, with each margin of which the valves were 

 in symphysis, or, as is more probable, by a double plate, divided by a 

 median suture. Test broadly infolded on the lower surface, thickened 

 and produced into a conspicuous and acute posterior spine. Posterior 

 margin incurved and produced into a short spine at the dorsal line. 

 Surface with a single strong carina on each valve. Abdomen consist- 

 ing of two somites of which the posterior is the longer. Post-abdomen 

 with a broad caudal plate, which is produced into a relatively short 

 telson. Lateral spines long and setaceous. 



Neptuni, Hall & Clarke, 1888; Pal. New York, vol. 7, p. 191, i)l. 32, 

 fig. 7; pi. 33, fig. 1. Hamilton. 



Dithyrocaris Neptuni, Hall, 1876 ; HI. Devonian Fossils, pi. 23, fig. 6, not 

 pi. 22, figs. 1-5 ; pi. 23, figs. 1-3. 



Dithyrocaris Neptuni, Packard; 12th Rept. U. S. Geol. Survey Territories, 

 p. 4.52, fig. 73. 



Dithyrocaris Neptuni, Etheridge, Woodward & Jones, 1887 ; .5th Rept. 

 Conim. Fossil Phyllopoda Pal. Rocks, p. 8. 



Neptuni, Etheridge, Woodward & Jones, 1888; 6th Rept. Comm. Fossil 

 Phyllopoda, p. 8. 



Oceani, Hall & Clarke, 1888; Pal. New York, vol. 7, p. 187, pi. 32, 



figs. 1-6 ; pi. 33, figs. 4-7 ; pi. 34, figs. 1-5. Portage. 



Dithi/rocaris Neptuni, Hall, 1876 ; lUust. Devonian Fossils, pi. 22, figs. 1-5 ; 



pi. 23, figs. 1-3. 

 Dithi/rocaris Neptuni, Etheridge, Woodward & Jones, 1887 ; 5th Rept. Comm. 

 Fossil Phyllopoda Pal. Rocks, p. 8. 



Oceani, Etheridge, Woodward & Jones, 1888 ; 6th Rept. Comm. Fossil 

 Phyllopoda Pal. Rocks, p. 8. 



stumsea. Hall & Clarke, 1888; Pal. New York, vol. 7, p. 193, pi. 32, 

 figs. 8, 9 ; pi. 34, fig. 2. Hamilton. 



stUHfea, Etheridge, Woodward & Jones, 1888 ; 6th Rept. Comm. Fossil 

 Phyllopoda Pal. Rocks, p. 8. 



(Dithyrocaris?) Veneris, Hall & Clarke, 1888; Pal. New York, vol. 7, 

 p. 193, pi. 33, fig. 3. Hamilton. 



(Dithyrocaris ?) Veneris, Etheridge, Woodward & Jones, 1888 ; 6th Kept. 

 Comm. Fossil Phyllopoda Pal. Rocks, p. 8. 

 NeoHmulua, Woodward, 1868; Geol. Mag., vol. 5, p. 1. Type Neolimulns 

 Julcatus, Woodward. 



