vou2.pt. 2.] A TAX0N0MIC STUDY OF THE SALPIDAE METCALF. 121 



dorsally into two groups of three and two respectively. This shows 

 that, as one would naturally expect, the condition with dorsally 

 approximated body muscles is secondary. If this is true for the 

 aggregated zooids, it is doubtless true also for the solitary individuals. 

 Thalia longicauda, with its regularly spaced body muscles in the soli- 

 tary form, is therefore to be regarded as more archaic than Thalia 

 democratica with its body muscles in the solitary form approximated 

 dorsally into two groups. 



Subgenus Thetys Tilesius, 1802. 



THETYS VAGINA Tilesius, 1802. 



Salpa tilesii Cutter, 1804. 



Dagysa strumosa Home, 1814. 



"Another species" Home, 1814. 



Salpa costata Quoy and Gaimard, 1824. 



S. bigibbosa Quoy and Gaimard, 1824. 



S. gibbosa Quoy and Gaimard, 1824. 



S. herculea Dall, 1872. 



5. infundibuliformis Quoy and Gaimard, 1824. 



(?) S. neapolitana Delle Chiaje, 1841. 



S. costata-tilesii Krohn, 1846, and more recent authors. 



Iasis costata-tilesii Herdman, 1891. 



Salpa vagina Ihle, 1911. 



To the subgenus Thetys may be assigned the single species vagina 

 (Salpa tilesii of most authors), the largest of the Salpidae. I have 

 nad two very good specimens of the solitary form besides several 

 degenerate specimens. Of the aggregated form I have had about 

 fifty specimens from six localities. Specimens of this species are 

 found in the United States National Museum collections as follows: 



Cat. No. 6438, U.S.N.M. (solitary form) , Albatross station D. 5441, 

 S. Fernando Point Light, west coast of Luzon; May 10, 1909; 186 

 fathoms; surface temperature, 87° F. ; one specimen. 



Cat. No. 6426, U.S.N.M. (aggregated form), Albatross station D. 

 3132, off Point Conception, California, March 14, 1890; 33 fathoms; 

 surface temperature, 55° F. ; one specimen. 



Cat. No. 6427, U.S.N.M. (aggregated form), Albatross station D. 

 2402, Gulf of Mexico, March 14, 1885; 111 fathoms; one specimen. 



Cat. No. 6515, U.S.N.M. (solitary form), Albatross station D. 5243, 

 Pujada Bay and vicinity, Philippine Islands; May 15, 1908; surface; 

 surface temperature, 84-85° F.; surface density 1.02453; eight 

 specimens. 



Cat. No. 6518, U.S.N.M. (tests of solitary and also aggregated 

 form), Albatross station D. 5242, Pujada Bay and vicinity, Philippine 

 Islands; May 14, 1908; surface; surface temperature, 85° F. ; sur- 

 face density, 1.02457; 44 specimens. 



Cat. No. 6552, U.S.N.M. (test) , Albatross station D. 5569, north of 

 Tawi Tawi, Philippine Islands; September 22, 1909; surface; sur- 

 face temperature, 83° F. ; one specimen. 



