ERYONICUS CZECUS. gl 
gastric region arranged in a longitudinal series behind the orbital sinus, one 
at the bifurcation of the cervical ridge, and one at the anterior end of the 
anterior branch of the cervical ridge. The subdorsal or branchial ridge of 
each side bears five spinules, and there is one spinule on the branchial area 
between the median and branchial carinse. The lateral carina, which runs 
from the external angle of the orbit to the posterior margin of the carapace, 
and is homologous with the lateral margin of the carapace in Polycheles and 
Willemoesia, bears sixteen spines arranged thus: 6—3—7; of these the last 
four are the largest. Below this lateral carina there are two longitudinal 
ridges on each side of the carapace, the upper of which extends from the 
outer side of the base of the second antenna almost to the hind border of 
the carapace, and is spinulose along the anterior third of its course ; the 
lower carina starts on the margin of the pterygostomian region one third 
of the way from the anterior end of the carapace, curves outward and 
extends back to the posterior margin of the carapace ; this carina is very 
prominent posteriorly, and bears five spines, decreasing in length from the 
first to the fifth, and followed by small denticles ; the anterior spines in this 
series are the largest on the body; on the line of this ridge the carapace is 
bent sharply inward and becomes horizontal. The internal orbital angle is 
furnished with a minute spine not in advance of the rostrum. The external 
orbital angle has a strong spine, the first of the lateral ridge. The orbital 
sinus is deep, and its posterior or blind end is broad and rounded. The 
ophthalmic lobes are armed with an outward-turned spine on their front 
margins. 
The abdomen is adorned with five longitudinal rows of spines, one 
median and two pairs lateral; the median or dorsal row is made up of 
one spine on the first abdominal somite, two on the second, third, fourth, 
and fifth, one on the sixth, and two on the proximal end of the telson; of 
the two dorsal spines on the second, third, fourth, and fifth somites, the 
anterior one is the longer, and is connected with the minute posterior one by 
an elevated ridge ; the single dorsal spine of the sixth somite is sharp and 
erect. The upper of the two lateral abdominal rows consists of a single spine 
just above the pleura of each somite from the second to the sixth, while 
the lower lateral row consists of one small spine on the upper portion of the 
pleurze of the second to the fifth somites. The pleure of the first abdominal 
somite are small, turned forward, and articulated with the hind part of the 
carapace ; the second, third, fourth, and fifth pleure are rounded, their mar- 
