372 W. G. Van Name — Bermuda Ascidians. 



These spicules are tetrahedral in form, with each angle prolonged 

 into a pointed ray or spine, and usually so placed about the zooid 

 that one point is directed radially outward. A few are also scat- 

 tered about in other parts of the test. 



Zooids with leather large branchial sacs with four rows of stig- 

 mata. Branchial aperture six-lobed, atrial plain. 



Echinoclinum verrilli, n. sp. 



Plate L. Figures 23, 24 and 25. 



The largest colony of this species which was obtained measured 

 about 1 2 mm across and about 3 mm in thickness. The zouids are 

 arranged in branching systems. 



The test is colorless and very transparent in the preserved speci- 

 mens. I have no notes upon its appearance in life. Though soft 

 and flexible, it is continuous and solid, and no such extensive cavi- 

 ties occur as is usual in Diplosoma. On the surface and immedi- 

 ately around the zooids, where, as already mentioned, most of the 

 spicules are situated, the test is very tough and membranous. Else- 

 where it is soft and gelatinous, and contains only a few scattered 

 spicules, and here and there a few bladder cells. 



I have not been able to distinguish any muscular processes 

 extending out from the zooids into the test, but it is almost impos- 

 sible to remove the zooids from the above mentioned tough mem- 

 branous layer of test which surrounds them. It adheres to the 

 mantle very closely at several points. One of these is about the 

 atrial aperture. In addition there are two small areas, one on each 

 side of the posterior part of the thorax, where the mantle and test 

 are very firmly united, but I have made out no vascular processes 

 extending out at these points. Sections of the thorax show that in 

 these places there is a concavity in the contour of the body wall, 

 and a corresponding projection of the common test into it, this 

 being the part which adheres to the mantle. 



The spicules vary much in size, the largest measuring about .15 mm 

 across from point to point. On each side of the thorax of the zooids, 

 these are small groups containing smaller spicules than those found 

 elsewhere. Apparently these are at the points above mentioned 

 where the mantle and test adhere together. In addition to the 

 spicules, the test contains some large, round, yellowish green cells, 

 Avhich are probably symbiotic algaa, as well as the usual small test 

 cells. 



The zooids are small (less than l ram in length in the contracted 



