CATALOGUE OF TUNICATA. 101 



Test usually soft, traversed by numerous vessels, with large terminal 

 knobs. 



Branchial sac large and well-developed, internal longitudinal bars 

 present. Stigmata numerous. 



Dorsal lamina in the form of a plain membrane. 



Tentacles simple, not more than 16 in number. 



Alimentary canal placed alongside the posterior part of the branchial 

 sac. 



Gonads on both sides of the body. 



Gemmation lateral from the bodies of the Ascidiozooids, and also 

 stolonial, from the ectodermal processes or vessels in the test. 



The Botryllids in the collection fall into the two closely allied genera 

 Botrylloidcs and Sarcobotrylloides. 



Botrylloides, M. Edw., 1842. 

 A new species and a variety are added to this genus. 



Botrylloides leptum, n. sp., PL Bot. I., tigs. 5 13. 



Colony thin, encrusting, spreading to form irregular lobed sheets of a 

 general light brown colour, with the Ascidiozooids darker. Specimens 

 about 6 cm. in length. 



Systems rather small, circular, elliptical, or short rows ; round the 

 edges of the colony meandering lines occur (fig. 5). Large areas of test 

 are free from systems. 



Test from 4 to 10 mm. in thickness ; grey, with numerous small, 

 closely-placed brown dots, which are the knobs on vessels. No bladder 

 cells, and no pigment masses, but very many rather large branching 

 vessels (figs 7 and 8). The test cells are small and numerous, and, in 

 some places, the matrix shows delicate fibrillation. 



Ascidiozooids 1 to 1-5 mm. long, with long axis parallel to surface. 

 Viscera alongside thorax. 



Mantle very thin and delicate, with many longitudinally running 

 muscle fibres. 



Branchial sac with 3 internal longitudinal bars on each side. The 

 stigmata are short and wide (figs. 9 and 10), and are 3 or 4 in a mesh. 



Dorsal lamina a plain membrane, rather narrow. 



Tentacles 4 large and 4 small, placed alternately (fig. 12). 



Dorsal tubercle a circular opening in middle of prebranchial zone. 



Alimentary canal on left side of branchial sac, with 10 well-marked 



