^^ REPORT ON THE TUNICATA OP PLYMOUTH. 



ClAVELiNA l-EPADirOEMis, McTntosh. Marine Invertebrates and Fishes of St. 

 Andrews, 1875, p. 54. 



— — Herdman. Fauna of Liverpool Bay, vol. i, 1886, 



p. 296, and Proc. Biol. Soc. Liverpool, vol. iii, 

 1889, p. 245. 



— — Cams. L. c, p. 476. 



Colonies compact, zooids numerous. 



Zooids more or less stout, moderately clavate, sliglitly compressed 

 fi'om side to side, without well-marked external differentiation into 

 thoracic and post-thoracic regions ; average height from a half to 

 three-quarters of an inch. 



Test gelatinous, perfectly hyaline and transparent. 



Thorax one third of the total body-length ; oesophageal region 

 short ; conspicuous opaque bands of a yellow, brown, or white 

 colour mark the position of the dorsal, ventral and anterior peri- 

 branchial sinuses. 



Branchial sac with about thirteen transverse rows of stigmata ; 

 horizontal membranes broad. 



Hahits. — Attached to rocks and stones (rarely to algae and the 

 backs of crabs, Miiller) at the bottom of the tidal zone ; seldom 

 extending into 10 fathoms water. 



At Plymouth fine colonies of this species have been found at 

 extreme low water on the north side of Drake's Island, near the 

 ''Bridge" under Mount Edgcumbe Park, in tide-pools among the 

 Renny Rocks, and in a few other localities. A few isolated zooids 

 have also been dredged occasionally in 4 to 5 fathoms water near 

 the Duke Rock, and, very rarely, in 10 to 15 fathoms off the 

 Mewstone and Penlee. 



On PI. II, fig. 1, I have represented part of the series of 

 languettes which extends along the dorsal median line of the 

 branchial sac, in order to display their method of connection with 

 the horizontal membraues. The languettes themselves are compa- 

 ratively narrow and slender ; they are compressed antero-posteriorly 

 and are not connected with one another by any trace of a longi- 

 tudinal lamina. 



The hoi'izontal (interserial or transverse) membranes are thin but 

 well-developed, and may project sufficiently for each one to com- 

 pletely cover the row of stigmata immediately behind it. The free 

 margins of these membranes are perfectly even ; they are not in 

 the least degree scalloped (festooned), and they show no trace of 

 marginal papilltB. 



