170 STALK-EYED CRUSTACEA. 
NOTOSTOMUS A. M. Epw. 
Ann. Sci. Nat., Zool., 6¢@¢ Sér., Vol. XI, Art. 4, p. 7, 1881. 
Notostomus fragilis Fax. 
Plate XLIV., Fig. 2, 2%, 2. 
Bull. Mus. Comp. Zodl., XXIV. 207, 1893. 
Dorsal line of carapace convex, and keeled from anterior to posterior 
margin, anteriorly produced into a short, acute rostrum, which does not 
exceed the eye-stalks in length; the dorsal carina is armed with seven or 
eight minute teeth on the anterior gastric region and the basal portion of 
the rostrum; lower margin of rostrum unarmed. A longitudinal carina on 
each side of the carapace begins near the orbit, above the infra-orbital spine, 
and runs back to the posterior margin ; another carina runs obliquely down- 
ward and backward, dividing the branchial from the hepatic region. The 
inferior lateral carina is obsolete except for a short distance behind the spine 
which lies near the anterior margin of the carapace behind the base of the 
second antenna. 
The abdomen is strongly compressed, the third, fourth, fifth and sixth 
segments dorsally carinated; the carina terminates in a small tooth at the 
hind end of the fourth, fifth, and sixth segments; on the fourth segment 
the carina is divided into two parts by a deep notch about two thirds of the 
distance from the anterior to the posterior margin of the segment. The 
telson is channeled on the dorsal side, and is tipped with two long spine- 
like setae. 
The eye-stalks taper from the base to the tip; their outer and upper mar- 
gins are nearly straight, but their inner and lower surfaces are swollen; on 
the inner side of each stalk, a little way behind the eye, there is a blunt 
tubercle. The eye itself is small and black. The integument of the eye- 
stalk is transparent, and when held to the light, discloses the optic ganglion 
within, giving off a nerve to the retina, and another to the tubercle on the 
inner side of the stalk. 
The basal segment of the antennule is armed with a very small but 
sharp external spine. The outer side of the second antenna, on the con- 
trary, is unarmed. The antennal scale is very broad, oval, and furnished 
with a small spine on the external border, near the distal end. The third 
