SUPER-ORDER V MALACOSTRACA 657 
Emmelezoe, Jones and W. Valves of carapace elongate, narrow, and with distinct 
ocular node; other cephalic nodes wanting. Surface with fine longitudinal raised 
striae. Abdomen unknown. Silurian. 
Sub-Order D. RHINOCARINA. Clarke. 
Carapace with a free rostrum and narrow median dorsal plate separated from the 
valves by a straight or slightly curving hinge at each side. Ocular nodes clearly defined, 
with a distinct optic pit at the swmmit. 
Family 1. BRhinocaridae. Clarke. 
Valves articulated by interlocking at the single point where they come in contact. 
Abdominal segments two to three. Posterior margin of carapace concave and spined. 
Rhinocaris, Clarke (Fig. 1376). Carapace smooth, with fine raised longitudinal 
striae ; divergent, branching furrows radiating back- 
ward from the eyes. Lateral carina very faint. 
Abdomen with two or three free segments, the last 
much longer than the others; all diagonally striated 
or chevroned. Caudal plate with a broad telson and 
two long and 
slender cercopods 
fimbriated on 
their margins. 
Middle Devonian; 
New York. 
Mesothyra, 
Hall and Clarke 
(Fig. Wee. 7): 
Carapace _ large, Hee LT. rlistactee Gcareee ors Gots ae 
valves distinctly Mesothyra Oceani, Hall. Portage Group York. A, E, Dorsal and lateral views of 
2 licks (Upper Devonian) ; Ithaca, New York. 4A, animal. £, D, Same of rostrum, en- 
interlocking at Bye. B, Hinge of right valve. 1/;. larged. C, Median plate, enlarged. 
point of contact. 
Lateral carinae strong, crenulated at the summit. Abdomen with two broad, exposed 
segments. Telson shorter than the cercopods, the latter setigerous. Upper Devonian ; 
New York. 
E 

Fic. 1376. 

Dithyrocaris, Scouler (Argas, Scouler). Very similar in aspect to Mesothyra, 
with the junction line of the valves overlapped by a (free ?) rugose ridge or narrow 
interstitial plate. Rostrum not observed. Devonian and Carboniferous; Scotland. 
Rachura, Scudder, known only from the abdomen and telson, is probably allied to 
Dithyrocaris, Carboniferous ; Illinois. 
Chaenocaris, Jones and W. Carapace valves with a very strong lateral ridge and 
without posterior spine. Carboniferous; Scotland and Belgium. 
Sub-Order E. DISCINOCARINA. Clarke. 
Sub-circular or oval shields with a triangular rostrum filling an anterior notch 
Surface ornamented with raised concentric lines. Substance chitinous. 
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