ISOPODS OF NORTH AMERICA. 523 



ANALYTICAL KEY TO THE SPECIES OF THE GENUS PSEUDIONE. 



a. Lateral parts or pleural lamella* of abdomen of female elongated, and covering to 



a great extent the pleopods. 

 b. Distal segment of the first lamella of the inarsupium produced posteriorly in a 



lobe. 



c. Inner branch of the pleopoda much larger than outer branch, elongate, and 

 pointed; surface roughened by irregularly transverse rugae. Pleural plates 

 of the last three segments of the thorax not developed as lamellae. First 

 incubatory lamellae with the distal segment produced in a lobe which is 



small and strongly curved inward Pseudione giardi Caiman 



</. Inner branch of the pleopoda a little larger than the outer branch, triangular 

 or ovate; surface smooth. Pleural plates of the last three segments of 

 the thorax developed as lamellae. First incubatory lamellae with the distal 

 segment produced in a lobe which is large and directed straight backward. 



Pseudione galacanthx Hansen 

 It'. Distal part of the first lamella of the marsupium not produced posteriorly in a 



lobe Pseudione furcata Richardson 



a'. Lateral parts or pleural lamellae of abdomen of female not elongated, but reduced 

 in size and short, not covering to a great extent the pleopoda. 



Pseudione curtata Richardson 



PSEUDIONE GIARDI Caiman. 



Pseudione giardi CALMAN, Ann. N. Y. Acad. Sci., XI, 1898, pp. 274-281, pi. 

 xxxiv, fig. 5. RICHARDSON, Proc. U. S. Nat. Mus., XXI, 1899, p. 869; Ann. 

 Mag. Nat. Hist, (7), IV, 1899, p. 337; American Naturalist, XXXIV, 1900, 

 p. 309. BONNIER, Trav. de la Station Zool. de Wimereux, VIII, 1900, pp. 

 299-300. RICHARDSON, Proc. U. S. Nat. Mus., XXVII, 1904, p. 78. 



Locality. Puget Sound on Pagurus ochotensis (Brandt). 



"Description of female. The single specimen, measuring 12 mm. in 

 length, was taken from the right branchial cavity of its host (Pagurus 

 ochotensis (Brandt)), and it is accordingly a dextral individual (Bopyre 

 droit Giard and Bonnier), though the outline of its body seems at 

 first sight to indicate a sinistral curvature from the concavity of the 

 right margin in the region of the posterior thoracic segments. Closer 

 examination, however, shows that the head and the abdominal region 

 are turned toward the left and that the pleopods of the right side are 

 longer than those of the left, as in a normal dextral individual, so that 

 the peculiar curvature of the body is in all probability merely an acci- 

 dental variation. 



''The specimen shows no traces of pigmentation. The dorsal surface 

 is flat or slightly concave; the ventral is convex, and is covered, except 

 in the region of the abdomen, by the greatly developed brood-pouch. 

 The dorsal swelling of the cephalic region which marks the position of 

 the stomach (cephalogaster) is very slight. An irregularly oval, some- 

 what convex area, the 'ovarian bosse,' is marked off by a groove on 

 each side of the first four thoracic segments on the dorsal surface. 



"The abdominal segments, six in number, are distinctly separated 

 from each other. The ventral surface of the abdominal segments and 



