474 LICHENOPORIDJE. 



the central spaces very narrow, linear; zooecia very 

 slightly prominent. 



L. HISPIDA occurs in two very different conditions. The 

 zoarium is either simple or composite, consisting of a 

 single disk, which is generally suborbicular and often 

 very convex, but occasionally more or less saucer-shaped ; 

 or of many disks united, so as to form rather large 

 masses, with many papillary prominences studding the 

 surface. In the saucer-shaped variety the edge of the 

 basal lamina is free and suberect, and incloses the celli- 

 ferous portion of the zoarium. "In its more usual state 

 the simple form is entirely adnate and a good deal raised, 

 the cells radiate very regularly from the central space at 

 the summit of the convex disk towards the margin, the 

 orifices are but slightly elevated, and the upper margin 

 is usually furnished with three spines, one central and of 

 considerable length, and two lateral and shorter. The 

 latter are often abortive, and the orifice is simply acu- 

 minate*. The pores (or ostioles) are smaller than the 

 zooscial apertures ; they cover the central area, and are 

 ranged in one or two lines along the interspaces. They 

 are all but universally stellate. 



The composite form seems to owe its origin to succes- 

 sive buddings from the margin (Plate LXVIII. fig. 4), the 

 cluster of distinct disks thus produced gradually coalescing 

 so as to constitute a massive zoarium, with a mamillated 

 surface. Very beautiful specimens of this kind occur : 

 I possess one from the Cornish coast which measures 1 

 inch in circumference, and is covered with about- thirty 

 of the characteristic eminences. The latter exhibit many 

 diversities : in some cases they are very small, thickly 



* In a young and beautifully developed specimen, I have noticed two 

 small denticles placed one on each side in front of the usual triplet ; in some 

 cases the latter is replaced by two long spines of equal size. 



