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IOWA ACADEMY OP SCIENCE Vol. XXIV, 1917 
of accuracy in description but the appendages are either wholly 
wanting or are represented by the proximal segments alone. 
The sides of the shrimplike cephalo-thorax are so strongly 
compressed that the postero-lateral portions of the branchiostegite 
are subparallel; the sides are longer below than above. The 
postero-ventral angle of the right branchiostegite is perfect, that 
of the left is partly broken. Transversely the dorsum is highly 
arcuate as far forward as the rostrum, wlpch ends in a short 
spine ; longitudinally the dorsum is very gently arched. The sur- 
face of the specimen is smooth, glossy, or polished in appearance 
and marked by greater and lesser punctge. The greater punctge 
are not very numerous and can be seen with the naked eye ; the 
lesser punctae are very numerous and can be seen only with the 
aid of a microscope. The region of the ophthalmic segment or the 
rostral region is not arcuate but flattened and slopes gently to 
the dorso-lateral angle. 
Extending from the posterior end of the cephalo-thorax to the 
transverse gastric sulcus there is a dorsal carina bearing a nar- 
row mesial threadlike keel ; anterior to the transverse gastric sul- 
cus it is continued as a low lamellar crest and terminates in a 
short, laterally compressed rostral spine. The hepatic sulcus (or 
sinus) begins at the base of the antenna, extends backwards along 
a slightly curved line for a distance of six millimeters thence 
bends abruptly upward at a right angle to the dorsal carina, for 
a space of four millimeters whence it bends forward in a short 
curve, then back upon itself postero-dorsally at a sharp angle, 
and finally, after describing a short semi-circle, it passes an- 
teriorly along the side of the dorsal carina as the gastro-dorsal 
groove. (See Plate Va, figure 1, gd.). There is but one spine on 
each side of the cephalo-thorax; each is located at the antero- 
lateral angle of the cephalic carapace and on a level with the base 
of the rostral spine. From this lateral spine a shallow but dis- 
tinct groove extends backward to within a millimeter of the 
hepatic sulcus and its course is almost parallel to the ventral 
margin of the cephalic carapace, — the two being approximately 
1.5 mm. apart. This groove bears a delicate threadlike ridge 
along its bottom. Beyond the hepatic sulcus and about 1 mm. 
dorsally a similar groove continues nearly to the end of the 
cephalo-thorax, its course being practically parallel to the dorsal 
carina. This may be called the cardiaco-branchial groove. It is 
