;i mimlier of the here mentioned species show plainly concentric lines of growth, 

 they on the other hand show a distinct radiate arrangement in Inuerxitila iiiuersd 

 and AiKirlliropoia luoiwdnn (PI. XXIII, ligs. 10 a, 11 a). These small plates which arc 

 only distinct in quite young zo(vcia are each i)rovided in the centre with a pore, 

 the edge of which has radiate rods, and to judge from Hi neks' drawing the front 

 surface in the following sjiecies descrihcd hy him is also divided into a number 

 of small plates each of which has a pore in its centre, namely, ^Lepruli<i<, I'alUi- 

 si(tna (from Madeira), Sc/)/ro/jorc//o cinctiporn Hincks, ^Scli.* cnnciiinn Hincks, Arlhio- 

 pouui circiniKild Mac Gill., Lcprnl'ut siibiiuinrrsd Hincks and Lep." giyas Hincks. 



In numerous species which appear in free colonies either the l)asal wall or 

 the frontal wall or both show a mode of calcification which we might call the 

 bilateral, as the wall in question is calcified in two lateral halves, which meet 

 in a longitudinal suture and as a rule each lateral half seems again composed 

 of a row of pieces the dividing sutures of which meet the longitudinal suture 

 oblicjuely. We may cite the structure of the liasal wall in Fliislni foliacen (PI. 

 XIX, fig. 9a) as an example of this form of cakilicalion. On this wall we find 

 two systems of extremely fine stripes, which meet under |)roximally directed angles 

 and divide the wall into two lateral halves, separated by a longitudinal suture; 

 the two halves are again composed of a row of pieces, and these arc .separated 

 l)y distally directed, slanting sutures wdiich end in the main suture. Each of 

 these lateral pieces is further joined to one of the pieces in which the respective 

 lateral walls are divided. We can be sure that the above-mentioned fine stripes 

 are lines of growth by treating the growing end of a branch with eau de Ja- 

 velle; for after this has dissolved the uncalcified parts, the basal wall of the 

 terminal zon^cium shows an angular incision which corresponds with the angle 

 between the two systems of stripes. This form of calcification which can also 

 present a number of modifications is for instance found in Fliislra Barleei, Fl. niem- 

 hritiuice<>-lriinc<tta, Fl. papyracea, Discoporii iwrriicosa, Dis. pdonnella, Dis. srabra. 

 Siiiillii)(i propinqna (PI. XIX, fig. 3 a), .S;n. rcliciihild, Sm. palinula (on the fronlai 

 wall), Arthroponid Cecili, etc. and no douhl it appears in most cases on the frontal 

 wall in species furnished with marginal pores, each of which serves as the starl- 

 ing-point for a suture which in most cases ends in the median suture. Still, a 

 median suture may be absent in very short zoa^cia and we find instead a nund)er 

 of fan-shaped, converging suture lines, as in Discopord pdvnneUn (PI. XIX, fig. 2 a). 

 With exception of the walls which are provided with si)ecially small pores 

 {ThaUimoporelld, Sleganoporella), all the surfaces (frontal walls, o(vcia), which are 

 furnished with scattered pores, are al.so provided with numerous sutural lines, as 

 these start from each pore, and except for those which end in the free edge of 



