DEVELOPMENT OF PALEOZOIC PORIFEROUS CORAL 420 



first circle of peripheral calices, have been observed mainly 

 from the epithecas of mature or nearly full-grown corallums, 

 represented on Plate XXVIII, figures 1, 2. In these ex- 

 amples the lines of growth are so perfectly shown that all 

 the stages are distinctly marked, and may be satisfactorily 

 studied. 



What is here considered as the second neanic stage is 

 represented on Plate XXVII, figure 3, showing the initial 

 corallite, with the first and second buds on opposite sides. 

 This process of alternate gemmation from the parent cell 

 continues until the circlet of calices is completed, as shown 

 in figures 4, 5, and 6. In this species the normal number of 

 peripheral calices is seven, making eight corallites in the 

 completed neanic corallum. The last cells to be formed are 

 (1) the sixth and seventh, budding from the anterior side of 

 the first calyx, and (2) the eighth, or posterior cell. Plate 

 XXVII, figure 12, represents the completed neanic corallum, 

 with the initial cell and six well-developed peripheral calices. 

 The eighth has just begun to fill up the space between the 

 second and third. It will be noticed that there is a direct 

 correspondence in the size of the calices to their relative 

 age. The first calyx is much the largest. Then, decreasing 

 serially, come the second, third, fourth, fifth, sixth, and 

 seventh, while the eighth is undeveloped. An inspection 

 of the upper surface of a mature corallum will thus usually 

 determine the order of successive calical additions. After 

 the appearance of the posterior, or eighth calyx, the corallum 

 commonly grows to double the diameter of the completed 

 neanic stage, resulting in the normal ephebic or mature con- 

 dition, as represented on Plate XXIX, figures 1, 2. Nearly 

 all the full-grown specimens found agree in this respect. 



A corallum rarely presents any departure from the normal 

 number of calices. Plate XXX, figure 1, is an example of 

 a variation in the number of peripheral corallites, for in this 

 specimen there are eight in the circle instead of the usual 

 seven. A variation in the opposite direction is shown in 

 another specimen having five well-developed corallites about 



