78 S. I. Smith — Crustaceans of the Atlantic Coast. 



10-5 to 17""" in length, and the females from 13 to 23™"^) had either 

 three or four teeth on the dorsal edge of the rostrum, and none at 

 the tip or beneath ; and this is evidently the normal rostral dentition 

 of the species, although the fourteen remaining specimens show con- 

 siderable deviation from this typical form. Of these fourteen speci- 

 mens, nine) ail females from off Nantucket, from the Bay of Fundy, 

 and from Halifax, Nova Scotia, and varying from 19 to 25"" in 

 length), have four teeth above and one beneath the tip, and three of 

 these nine, all females from the Bay of Fundy, and each about 

 23°"" in length, have the inferior tooth so near the tip that the tip is 

 best described as bifid ; one female, 22""" long, from the Bay of 

 Fundy, is similarly armed at the tip but has only three teeth above ; 

 one female, 16"'™ long, from Halifax, Nova Scotia, has five distinct 

 teeth above but none below; while three males, 12 to 13 '5""" long, 

 from Casco Bay and Cashe's Ledge, have only two teeth above. 

 This would seem to show that a tendency to an increase in the 

 number of rostral teeth is characteristic of the females, while the 

 reverse is the case in respect to the males. 



The usually very constant arrangement of the terminal spines of 

 the telson is occasionally subject to variation, which apparently fol- 

 lows the same tendency in the sexes as the variation in the number 

 of rostral teeth, although the number of observations in either case is 

 too small for a reliable generalization. Of forty-eight specimens in 

 which the tip of the telson was specially examined, forty-five (among 

 which the males varied from 12 to 17""" in length, and the females 

 from 14 to 25"'"'), had the normal number of terminal spines; that is, 

 a short one at the lateral angle each side, two much longer ciliated 

 ones in the middle, and, between these and the lateral spines each 

 side, a still longer and stouter spine, making six in all (Plate IX, 

 figure 7). Of the remaining specimens, a male 17""" long, from the 

 Bay of Fvmdy, has but one median ciliated spine, so that there are 

 only five in all (Plate IX, figure 6) ; and yet there is not the slightest 

 appearance of this irregularity being due to injury, and the specimen 

 is in all other respects perfectly normal. A female 20'5'"™ long, from 

 the Bay of Fundy, has nine spines, of which the three median are 

 ciliated (Plate IX, figure 4) ; there is a little irregularity in the 

 spines, apparently due to some slight injury. Another female 10'""' 

 long, from Halifax, Nova Scotia, has also nine spines, of which the 

 five central ones were probably ciliated, although, apparently on 

 account of the imperfect state of preservation of the specimen, I was 

 able to discover cilia on only a part of them, as shown in the figure 



