214 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 5 



Atlantic and Pacific specimens of G. oerstedii are much alike. Yet, in 

 an extensive series from both oceans, the vast majority, with rare excep- 

 tions, of the Pacific representatives of the species has a common type of 

 telson which, for purposes of reference, is here distinguished as the Pacific 

 type, as compared with an Atlantic type. Rarely does any Atlantic repre- 

 sentative of G. oerstedii tend to exhibit any inclination toward developing 

 the Pacific type of telson. However, there are enough specimens, although 

 very few with the opposite type in the waters of each ocean, to preclude, at 

 least in the light of our present knowledge, giving them a more definite 

 nomenclatorial status than here attempted. 



The Atlantic type of telson has been well figured and described by 

 Bigelow (1901, p. 152, fig. 1). There is a distinct, wide, V-, almost 

 U-shaped notch or interval between the submedian and intermediate teeth 

 of the telson margin; in the apical angle of this notch there is a well- 

 developed lobule anterior to the level of the extremity of the intermediate 

 spine. Very rarely is the posterior margin of this lobule on, or does it ap- 

 proach, the level of the extremity of the intermediate tooth. In these rare 

 cases the notch or interval between the submedian and intermediate teeth 

 tends to become more or less obliterated, and the outer margin of the sub- 

 median tooth and the inner of the intermediate tooth where they proxi- 

 mally approach one another are separated by little more than the width of 

 the intervening lobule. In all cases, however, there is always a noticeable 

 offset or separation between the major (longitudinal) axes of both teeth, 

 even though the trend of both may be more or less parallel. In no case is 

 the lobule situated up on the outer margin of the submedian tooth wholly 

 behind or posterior to the level of the extremity of the intermediate one. 



In the Pacific type of telson, the interval between the intermediate and 

 submedian teeth is wanting and the lobule that separates the intermediate 

 from the submedian tooth in the Atlantic forms is less distinct and scarce- 

 ly more, in many cases, than an irregularity of the outer margin of the 

 submedian tooth just before it passes over into the outer margin of the 

 rudimentary intermediate tooth. This reduced lobule is so placed that it is 

 situated posterior to the level of the extremity of the intermediate tooth. 

 I have seen one Pacific specimen in which a part, but not the whole, of this 

 lobule seemed to be behind the level of the extremity of the intermediate 

 tooth, but this is no doubt of exceedingly rare occurrence. A lobule which 

 is part before and part behind the intermediate tooth is also to be seen in 

 some of the small and near juvenile Atlantic specimens of G. oerstedii. 

 Thus we see in some of the small specimens on both coasts some conver- 



