NO. 1581. ADDITIONAL NOTES ON THE A RGULID.E— WILSON 419 



posterior border of the basal joint and a still long-er one farther in on 

 the ventral surface of the carapace close to the mid -line. 



Of the swimming legs the first pair only are developed, the others 

 being immovable stumps. This first pair consists of two basal joints, 

 the distal one uuich the smaller and armed with spines on its ventral 

 surface, and two rami. The endopod is three- jointed, each basal joint 

 armed with a long spine at its distal end and shorter ones on its ven- 

 tral surface, the terminal joint ending in two short spines. The 

 exopod is one-jointed, with bristles along its anterior margin and two 

 long nonplumose setiv at the tip. The leg stumps of the other pairs 

 show plainly the division into endopod and exopod, the latter of which 

 is tipped with two short spines, the former with only one, while both 

 are covered on their ventral surface with small spiny hairs. 



The internal anatomy is similar to that of other species already 

 described. The digestive tract is not as well formed as in the <wieri- 

 eaniis larva, and there is only the faintest trace of the shell glands in 

 front of the side branches of the stomach. The chitin rings in the 

 posterior lobes of the carapace are prominent and already possess the 

 same shape as in the adult, and so are characteristic of the species. 



The only other part deserving special mention is the skin glands. 

 In the american us larva there was only a single small group of these 

 glands on either side near the posterior edge of the carapace lobes. 

 In the present larva no' skin glands at all are visible on first hatching; 

 very small ones afterwards appear in the posterior carapace and the 

 abdomen. 



IV. ARGULUS APPENDICULOSUS, new species. 

 Plate XXXII, %8. 23-30. 



Carapace orbicular, longer than wide, projecting slightly anteriorly, 

 with broad and well-rounded posterior lobes, which just reach the 

 abdomen in the male but fall a little short in the female. Posterior 

 sinus broad, its sides slightly divergent, showing in dorsal view the 

 bases of the posterior legs on either side of the last two or three 

 thorax segments. Ej-es small, situated far forward and well separated; 

 cephalic area nearly as wide posteriorly as anteriorly, with evenly 

 rounded sides. Chitin rings in the lobes of the carapace large and 

 well defined, having the same general pattern as in A. catostoin!^ 

 americamis^ and versicolor^ namely, an outer larger, semilunar ring 

 with a much smaller spherical one inserted in its inner border near the 

 anterior end. 



In the present species the anterior portion of the outer ring, in front 

 of the spherical ring, is larger than usual and reaches almost to the 

 center of the disks of the first maxillipeds. 



The spherical rings are relatively smaller than in the species men- 

 tioned and are buried more deeply in the sides of the large rings. 



