NO. 19S9. A8CIDIANS FROM NORTHEASTERN PACIFIC— RITTER. 489 



eumyota comes from the eastern coast of South Amierica. But since 

 the beginning of my studies I have had the opportunity, thanks to 

 Hartmeyer, to examine specimens from Yokohama and identified 

 by him as jaiionica, and do not now hesitate to regard my specimens 

 and his as being of the same species ; nor do I seriously question that 

 both sets of specimens are the same as the ones examined by Ilerd- 

 man; that is, that all are japonica. It appears from a late paper by 

 Hartmeyer (1906) that he found no difficulty in the way of identi- 

 fying his Japanese animals as Herdman's species. There are, how- 

 ever, a few points, two particularly, in which my observations do 

 not quite agree with Herdman's description, and since it was just at 

 these points that I formerly thought my specimens agreed more 

 closely with eumyota than with japonica I have thought it desirable 

 to present a few drawings and write explicitly of these matters. The 

 first to be noticed is the mantle musculature. Herdman called 

 special attention to the peculiarity of this but his statement and 

 figure need modifying somewhat to make them apply to the specimens 

 which I have examined. He says, "In Corella japonica the muscula- 

 ture is very strongly developed along the dorsal part of the left side, 

 while in Corella eumyota there is no such disproportionate develop- 

 ment" ; and his figure 2, plate 26, illustrates this statement. In all the 

 specimens examined by me as well as in those from Yokohama and 

 identified by Hartmeyer as japonica and those belonging to the U. S. 

 National Museum collections, while the muscle fibers are undoubtedly 

 well developed along the dorsal ridge, they are not particularly more 

 so there than all the way around an elliptical area corresponding to 

 nearly the entire left side ; in fact in the specimen from which figures 

 28 and 29 were drawn the fibers are distinctly more numerous and 

 quite as strong all along the ventral edge of the area as along the 

 dorsal. In the specimens which I have examined the area of rela- 

 tively heavy mantle muscle fibers might be characterized as a dis- 

 tinct patch of elliptical shape corresponding in general to the left side 

 of the animal; and one of the strilving things about this patch is the 

 sharpness of its boundary as determined by the abrupt ending of the 

 muscle fibers along nearly the whole circumference. Figures 29 and 

 28, the first of the left, the second of the right side of the same indi- 

 vidual, illustrate this. The abrupt termination of the more or less 

 radially disposed fibers on the dorsal and posterior edges is clearly seen 

 in the figures, while the ends along the ventral and anterior edges can 

 only be inferred from the fact that the fibers are present on the left 

 side and do not pass over on to the right side at all. In some speci- 

 mens the circumference of the muscle "patch" is as distinctly visible 

 all the way around on the left as it is in figure 29 along the posterior 

 end. 



