486 LICHENOPORIDjE. 



crust having its own slightly expanded base. Occasion- 

 ally fresh disks are produced towards the dflgc of the ori- 

 ginal crust, which increase the area of the colony. Gem- 

 n^ation takes place, to a limited extent, from the surface 

 of the maraillary risings, as well as from the crust (Plate 

 LXIII. fig. 5); but there is never any distinct branching 

 as in the preceding species. The rows of cells are chiefly 

 confined to the rounded top of the mamillae, radiating from 

 the base to the summit ; but in some cases they extend 

 to the very edge of the border of the disk. They are very 

 slightly raised, and separated by mere superficial furrows, 

 and never form erect and prominent lamellae, such as we 

 find in D. stellata. Of the largest specimen which I have 

 seen, the longer diameter is nearly f inch, and the shorter 

 about ^ inch. This form connects the present group very 

 closely with the Lichenopora* . 



The foregoing account is based on a most interesting 

 series of specimens, for which I am indebted to the kind- 

 ness of Mr. Peach. 



HABITAT. On large stones from deep water. 



LOCALITIES. Shetland (Jameson and Prof. E. Forbes) : 

 ibid., brought up by the fishermen's lines from about 80- 

 100 fathoms in the Out Haaf (C. W. P.). 



Doubtful Species. 



TUBULIPORA HYALINA, Couch. 

 TUBULIPOEA HYALINA, Couch, Corn. Faun. iii. 108 : Johnst. B. Z. od. 2, 276. 



Zoarium adnate, semitransparent, membrane-calcareous . 

 Zocecia distinct, tubular, erect, arranged in one or two 

 circular rows round a plain centre ; orifice unarmed and 

 frosted. 



* D. truncata resembles in many respects the Semimulticavea (Domopora) 

 tuberculata of D'Orbigny, which is evidently a kindred form (Pal. Fran<;. 

 terr. ort-t. p. 980, pi. 648. figs. 1-4). 



