210 C. E. Beecher — Development of a Paleozoic Poriferous Coral. 



The initial cell occiqtie.s the central position, and forms the boss or 

 apex of the basal ejiitheca. The first bud is nearly on a plane with 

 the base of the initial cell and is the one nearest the apex. The 

 second and successive buds are respectively more distant, and at a 

 higher level. Specimens having broad surfaces of attachment to 

 foreign objects have these distinctive features of the epitheca obliter- 

 ated, and the only guide to the order of the corallites then lies in 

 their comparative size and position on the upper surface of the 

 corallum. 



General conclusions. — The first feature to be noted in the develop- 

 ment of a poriferous coral, as here described, is the simple cyathi- 

 form character of the initial corallite. This nepionic stage is 

 without mural pores, and has an epitheca over the entire exterior of 

 the cup. The septal lines become developed toward the end of 

 this stage. These features are in harmony with the young of many 

 paleozoic corals, such as Cladochonus, Aidoiyora, or Syringopora, 

 and clearly indicate a primitive, simple, and imperforate ancestry 

 for the Perforata. A similaf origin and development obtains in 

 Pavosites, as may be seen from the figure of a young colony of P. 

 Porbesi, var. occidentalis, given by Professor Hall.* 



The first nealogic stage, represented by the primitive corallite 

 with one bud, is the first transition towards both a compound and a 

 perforate coral, Plate IX, figure 9. This stage has two calices, mak- 

 ing it a comj)Ound coral, and has an opening through the cell walls 

 or connecting channel between the corallites, forming the first mural 

 pore. The manner of growth and the structure of the corallum at 

 this stage are suggestive of Atdojwnr, and should be given consider- 

 able significance. The visceral cavities in Atdopora are confluent, 

 and rudimentary septa or lines of spinules are often present. Poni- 

 ingeria has a growth resembling Aulopora and Syringojiora. It is 

 without pores on the portion where the corallities and buds are free, 

 but when these are in juxtaposition at their bases, mural pores are 

 developed. The upward groAvth of the initial cell of P. lenticulare 

 proceeds but a short distance before the circlet of peripheral coral- 

 lites is completed. Thus at this stage there are at least seven mural 

 pores opening into the primary calyx. If this tendency to the 

 formation of numerous buds persists throughout the upward growth 



* Indiana Geol. and Nat. Hist., 11th Rept. of tlie State Geologist, pi. i, figure 12, 

 1881. 



