(50 



BKITISH TITN1CATA. 



stout and widely separated ; the tubes are wide, well 

 produced, and terminal ; they are placed rather near 

 together, the atrial being scarcely at all lateral ; and 

 their walls are rather thick like the upper portion of 

 the mantle. 



The branchial sac (fig. 45) is remarkable for the 

 simple arrangement of the secondary vessels, which 

 are much less curved and sinuous than usual, the 

 approximation to the spiral type being very obscure 



.. - 





FIG. 45. Part of branchial sac of Molgula inconspicua. Much enlarged. 



but nevertheless quite determinable ; the primary 

 vessels are pretty distinct, and the radiating ones 

 more simple and parallel than in most of the species, 

 and there are four or five membranous rods on each 

 side of the folds, which are strongly arched ; the endo- 

 style is equally deeply curved and is long; the oral 

 lamina is short, the space between the mouth and 

 branchial tubercle being rather contracted ; it is 

 narrow, smooth, and a little widened as it approaches 

 the oral orifice. The tentacular filaments are bipin- 



