230 THE AMERICAN NATURALIST. 
č. Head and segments of thorax with not less than two pairs 
of spines to the segment. 
d. Head with one large median spine on the anterior part 
of the head in front of the eyes. 
Arcturus intermedius Richardson, A, 10 fms. (See Fig. 11, p. 229.) 
a’. with three spines on anterior part of head in front 
at eyes. 
Arcturus murdochi Benedict, A, 13% fms. 
a’. End of terminal abdominal segment without notch. 
. Thorax without spines above the epimera. 
Arcturus glaber Benedict, A, 55 fms. 
&. Thorax with spines above the epimera. 
c. Terminal segment of abdomen armed with a long median 
terminal spine, projecting beyond the end of the segment. 
Arcturus floridanus Richardson, S 
c. Terminal segment of abdomen not armed with long median 
terminal spine. 
. Four anterior segments of thorax with spines or tuber- 
cles. Middle surface of abdomen with prominent 
spiny projections. With conical lateral projections. 
Epimera pointed. 
Arcturus baffini (Sabine), AV, 110-150 fms. 
d’. Four anterior segments of thorax without spines or. 
tubercles. Middle surface of abdomen without any 
indication of prominent spiny projections. Without 
conical lateral projections.  Epimera less pointed. 
Arcturus feildeni Miers, JV, 30 fms. 
Genus Astacilla Fleming. 
a. With eyes. Head excavate in front without rostriform point. Fourth 
thoracic segment subcylindrical. Terminal abdominal segment with 
a prominent, subacute tooth on each side, above the middle, directed 
outward and backward ; extremity obtuse. 
Astacilla granulata (G. O. Sars), JV, 7-250 fms. 
a’. Without eyes. Head with a rostriform point in front between the 
antennule. Fourth thoracic segment wider at the anterior end, and 
tapering to the posterior end. Terminal terim segment with a 
pair of teeth on each side ; extremity acu 
Astacilla ceca Benedict, JV, 1825 fms. 
