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ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 21 



As recently as Rathbun (1925, p. 18), the definitive character relied 

 upon in separating Stenorynchus debilis from S. seticornis was the pres- 

 ence of a small supplementary spine on the basal antennal article of the 

 former. Since a figure of the male copulatory appendage of S. seticornis 

 has been available from the time of Brocchi (1875, pi. 19, fig. 176), it 

 is surprising that no one has compared with it the corresponding member 

 of S. debilis. The male first pleopod of S. debilis (Plate B, fig. 7) shows 

 good differentiation from that of the Atlantic species, and may be consid- 

 ered a specific character. 



Subfamily OREGONIINAE, new subfamily 



Inachinae Alcock, 1895 (part: Oregon ia) +Pisinae Alcock, 1895 (part: 



Hyas and Chionoecetes) . 



Male abdomen terminally broadened, last segment subquadrate or 

 transversely ovate, invaginated into sixth segment, its outer border 

 emarginate or introverted. 



Male first pleopod lanceolate, longitudinally grooved, provided with 

 numerous filamentous setae, and having a bulbous base. 



In erecting the subfamily on the above two characters no reference 

 is made to orbital configuration, differences in which have led to the 

 previous wide systematic separation between Oregonia on the one hand 

 and Hyas and Chionoecetes on the other. It will be noted that as one 

 proceeds from Oregonia to Chionoecetes, the exorbital spine tends to be 

 absorbed in the laterally expanded hepatic region, the sides of the carapace 

 to become vertical and delimited from the dorsal surface by a sharply 

 defined ridge. It is actually more difficult to reconcile the orbit of 

 Oregonia gracilis with that of O. bifida than it is to relate that of 

 O. bifida to the remainder of the series. 



The pleopods of Chionoecetes are not as different from those of 

 Oregonia and Hyas as would at first appear, due to the fact that the 

 Chionoecetes species, with the exception of C. opilio, are represented in 

 the accompanying figures (PI. I, figs. 5-9) by young specimens. Examina- 

 tion of the pleopods of young C. bairdi, C. tanneri, and C. angulatus 

 reveals more filaments than shown, some of which are arranged in sup- 

 plementary rows. The linear opening is present as a linear groove in the 

 other genera; whether it is open throughout its length or only at the end 

 could not be ascertained. The bulbous base, not shown, is a common 

 character. 



