50 BRITISH TUNIC ATA. 



thin and transparent, free or attached only at the 

 tubes. Alimentary canal largely developed, forming 

 two loops, both of which extend the entire width of 

 the body ; the liver of a pale green colour. Eepi-o- 

 Jnrfirr or<jn n of the right side fusiform, lying upon the 

 rectum within the lower loop. 



Longest i.lunui'ter three-eighths of an inch. 



Hab. ? 



SCOTLAND. Hebrides. 



First record. Alder & Hancock. 



We have seen only a single individual of this well- 

 marked species (figs. 38 and 39), and unfortunately the 

 internal parts were much injured, so that many of the 



FIG. 38. FIG. 39. 



FIGS. 38 AND 39. Test of Molgula valvata. 38, side view: 39, as seen 

 from above. Three and a half times natural size. 



characters could not be determined. The external 

 features, however, are sufficiently distinct, though they 

 resemble to some extent those of M. oculata, to which 

 the present species is undoubtedly closely allied. It is 

 distinguished, nevertheless, from that species by the 

 membranous valvular expansions within which the 

 tubes are placed. In M. oculata the margins of the 

 tubular area are not produced, while in M. valvata 

 they form two distinct membranous folds of consider- 

 able width which extend from near the ventral margin 

 to about two-thirds across the body ; these folds are 

 approximated between the tubes and are separated a 

 little in their immediate vicinity, so that here as well 

 as in M. oculata the perforated tubes simulate a pair of 



