66 
S. I. Smith — Crustaceans of the Atlantic Coast. 
however, the number of teeth varies from three to five above and 
from two to six beneath, although the extremes of these variations 
seem to be of rare occurrence, as the accompanying tabular summary 
of the result of the examination of one hundred and fifty-nine speci- 
mens shows. 
This result is, perhaps most noticeable for showing the constancy 
of what seems a very trivial character, for, among all the specimens 
examined, not one varies more than a single tooth either above or 
below the most usual number upon the dorsal carina and only two 
specimens (the last in the table) exceed this amount of variation in 
the number of teeth in the ventral edge of the rostrum. 
One specimen, not included in the above summary, has the rostrum 
slightly distorted and bifid at the tip as seen from above, — a pecu- 
liarity undoubtedly due to injury, though there is nothing but a 
slight lateral distortion to indicate such a cause. 
The two spines of the anterior margin of the carapax are usually 
both well-developed, but the inferior one (the pterygostomian) is 
occasionally very minute or even entirely obsolete. This obsolescence 
was noticed only in adult males, and is apparently an approach to 
the usual entire disappearance of the same spines among the old 
males of Hippolyte polaris. 
The dorsal aculei and terminal spines of the telson appear to be 
very constant in character and number. Among seventy-five speci- 
mens examined with reference to the dorsal aculei of the telson, 
sixty-nine had either four or five pairs, or four upon one side and five 
upon the other. Of the six remaining, four are young and have less 
than the normal number for adults, a male 15 mm long and a female 
16'5 mm having only three pairs of aculei each, another male 15 mm and 
a female I7 mm having each three on one side and four on the other; 
while a male 32 mra long has also less than the normal number, having 
three on one side and four on the other, and a female 27 mra has more 
than usual, having five upon one side and six upon the other. Fifty 
specimens examined with reference to the armament of the tip of 
the telson all had the normal number of spines, — two slender and 
ciliated ones in the middle with two stouter ones each side. 
The largest specimens examined were taken in the Bay of Fundy, 
the largest males being 39 mm long and the largest females 50 mra . 
The only specimens I have seen carrying eggs were collected at 
Eastport, Maine, in April, 1876, by Messrs. Merriam and Wilson. 
Among over a hundred adult females taken from July to late in 
October, none were carrying eggs. 
