CAM15ARUS. 95 



of hand with two or three rows of depressed ciliate tubercles; fingers costate 

 and punctato-lineate, gaping, inner margins with rounded tubercles ; mov- 

 able finger incurved ; carpus punctate above, armed with an acute median 

 internal spine and two inferior spines (a large median and a minute external). 

 In some specimens there are one or two small antennal basal tubercles. 

 Meros smooth without, two obliquely disposed superior sub-apical spines; 

 of the biserial inferior spines only a few of the distal ones in each row are 

 developed. Distal end of second pair of legs ciliate. Third segment of third 

 pair of legs hooked. First pair of abdominal appendages short, reaching to 

 the base of third pair of legs, thick, split for a short distance from the tip ; 

 outer part longer than the inner ; tips recurved, brown and horny. 



Female. Fingers less widely gaping, outer one ciliate within at base. 

 Abdomen broader. Sternum between fourth thoracic legs smooth. Annulus 

 ventralis a transverse ridge, thickest in the middle, where there is a rounded 

 tubercle divided longitudinally by a sinuous groove. Between the ridge 

 and the sternal plates of the fourth pair of legs there is a deep transverse 

 fossa. 



Measurements of a male, form I. Length of body, GO mm. Length of 

 carapace, 30 mm. Length of abdomen, 30 mm. From end of rostrum to 

 cervical suture, 20 mm. From cervical suture to posterior border of cara- 

 pace, 10 mm. Length of rostrum, 10 mm. Breadth of rostrum at base, 

 4 mm. Length of rostral acumen, 3 mm. Width of areola, 1.5 mm. Length 

 of antenna 1 , GO mm. Length of chela, 25 mm. Breadth of chela, 12 mm. 

 Length of movable finger, 17 mm. Internal border of hand, 7 mm. 



In one specimen, a male, form I., the fingers are very much elongated, 

 not gaping at base. The length of the internal border of the hand in this 

 specimen is 7.5 mm. ; the length of the movable finger, 21 mm. 



Locality. Irondale, Mo. Collected by E. Harrison. 



This species resembles O. rusticits in its general form. The male ap- 

 pendages, as well as the annulus ventralis of the female, however, are very 

 different from those of any previously described species. The male ap- 

 pendages approach in form those of C. propinquus more nearly than any 

 other, but in that species these appendages are more deeply bifid, and 

 not recurved. 



The second form of the male is unknown. 



