64 WALTER GARSTANG, M.A. 



Branchial sac with about thirteen transverse rows of stigmata; 

 horizontal membranes abroad 



Habits. — Attached to rocks and stones (rarely to algse 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 

 Eenny 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. 1,1 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 

 membranes. The languettes themselves are comparatively narrow 

 and slender ; they are compressed antero-posteriorly and are not 

 connected with one another by any trace of a longitudinal lamina. 



The horizontal (interserial or transverse) membranes are thin but 

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

 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 

 papillae. 



2. Pycnoclavella, gen. nov. 



Der. — Ttvitvot, closely united. 



External appearance. — Zooids small and delicate, clavate, arising 

 by slender stalks from a more or less thick, basilar mass of test- 

 substance. 



Body consisting of a small thorax, a slender, often greatly elon- 

 gate oesophageal region, and a more dilated abdomen, the greater 

 part of which is imbedded in the basilar mass of common test. 



Test thin and delicate around the thorax, thicker and firm in 

 the foot-stalks, dense and cartilaginous throughout the basilar mass ; 

 the latter is traversed in all directions by stolonial tubes, some of 

 which even extend and branch in the oesophageal region of the 



