V0D.2.PT. 2.] A TAX0N0MIC STUDY OF THE SALPIDAE METCALF. 109 



The neural gland (fig. 103) consists of a postero-modian chamber, 

 which pushes forward on both sides, beneath the ganglion, to form 

 pouches in the usual positions of the hollow disks. There is but one 

 lateral duct leading from the neural gland to the pharyngeo-atrial 

 chamber. This is very wide. 



RELATIONSHIPS OF THE SUB-GENUS IASIS. 



Iasis is very distinct from all of the other subgenera. Like most of 



the species still to be discussed, it has a reduced number of body 



muscles. It has also a reduced oral musculature, as have also Thetys, 



Pegea, Thalia, and Traustedtia. Its atrial musculature is most like 



that of Thalia. The form of the body in the aggregated zooids is 



considerably like that in the aggregated forms of the true Salpae. 



The gut resembles that of Ritteria in being a loop in the solitary form 



and a fairly compact "nucleus" in the aggregated zooids. The eye 



of the solitary form is essentially of the ordinary horseshoe type, 



though distorted in form. In the aggregated zooids the larger eye, 



though very compact, shows the usual proximal and distal portions, 



as seen hi the other species of the family thus far discussed. Its 



neural gland is peculiar. There are usually five embryos present in 



the aggregated zooids, showing different stages of development. It 



is difficult to draw confident conclusions as to the relationships of 



Iasis. I place it as an aberrant form, somewhat intermediate between 



Ritteria and the most divergent forms, Thetys, Thalia, Pegea, and 



Traustedtia. 



Subgenus Thalia (Blumenback (?), 1810). 



This subgenus includes the species democratica and longicauda 

 (Jiagellifera of most authors). The former is the most widely dis- 

 tributed and most abundant of all the species of Salpidae. The latter 

 is a rare species which has never been adequately studied. The 

 species democratica may be taken as the type since it was the first 

 described and is by far the best known. 



THALIA DEMOCRATICA (Forsk&I, 1775). 



Salpa democratica ForskAl, 1775. 



S. mucronata ForskAl, 1775. 



(?) Thalia lingulata Blumenblach, 1810. 



Salpa spinosa Otto, 1823. 



S. pyramidalis Quoy and Gaimard, 1826-1834. 



Biphora mucronata Costa. 



B. democratica Costa. 



Dubreuillia cirrhosa Lesson, 1830. 



Salpa democratica-mucronata Krohn, 1846. 



S. cabotti Desor, 1851. 



Thalia democratica-mucronata Herdman, 1891. 



Salpa mucronata Apstein, 1894,6. 



S. democratica Heider, 1895. 



