102 



BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



agree and none correspond to StreifTs description in the character 

 of the oral musculature. StreifTs work on other species is so vcry 

 accurate that one can not think his observations so erroneous upon 

 this form. His account, as it stands, does not agree with conditions in 



i.rn. 



Fig. 90.— Iasis zonaria, solitary form, seen from the right sidk. The mantle is shrunken atvat 

 from the test on both dorsal and ventral surfaces. x \\ diameters. (drawn by hoyt s. 

 Hopkins.) 



my specimens, but his accuracy as an observer must not be impugned. 

 There is some confusion here. May it be that Streiff had specimens of 

 Herdmann's "Salpa nitida," and this form thus proves a distinct 

 subspecies ? The body muscles of StreifTs specimens were much 



broader than those Herdmann 

 figures. 



There is a single strong 

 sphincter muscle in each lip 

 (fig. 91). At the angles of 

 the mouth their ends are 

 united and run back a short 

 way together, forming an 

 oral retractor muscle. These 

 sphincter muscles lie at the 

 edges of the strongly inturned 

 xips (fig. 92). Each is inter- 

 rupted on the mid line. Fur- 

 ther forward on the oral si- 

 phon, and separated by a 

 considerable interval from the 

 tiui 1 sphincters, there is, on 

 each side, a muscle (xx) of dif- 



FlG. 91.— IASIS ZONARIA, SOLITARY FORM, DORSAL VIEW OF ... 



anterior end of body, x 3j diameters. (Drawn ferent histological appearance, 

 by hoyt s. Hopkins.) opaque and browner in speci- 



mens preserved in either alcohol or formalin. These lie at the lateral 

 angles of the flattened oral siphon and extend but a short distance 

 onto the flat dorsal and ventral surfaces of the oral siphon. In a 

 few of my older specimens, neither the largest nor the smallest, the 

 muscle is interrupted at the angle of the siphon, making two half 

 muscles instead of one continuous one. The second sphincter muscle 



