C. E. Gordon — Early Stages in Paleozoic Corals. 123 



other " primary septa," (Duerden) ; (S) secondary septa. The 

 subscripts indicate the order of appearance. 



Figure 18 is a portion of figure 11 and is figure IT inverted. 

 The lettering in this case indicates the author's interpretation 

 of the value of the septa. (P v ) "cardinal septum" (author); 

 (Pa,) " counter septum " (author) ; (P) " alar septa " (author) ; 

 (S) secondary septa. The subscripts indicate the order of 

 appearance. . Note that the cardinal and counter septum are 

 reversed and that the number of primary septa are reduced by 

 two. 



Duerden, from his wide acquaintance with modern corals, 

 makes the statement that no living coral presents such a mesen- 

 terial (septal) sequence as L. jyroliferum, yet it bears the 

 closest resemblance to what is found to be characteristic of 

 Zoanthoid polyps, except that the mesenterial increase takes 

 place in only two exocoelic chambers in these forms, while, as 

 Duerden would have it, in L. proliferum it is carried on in 

 four such chambers. Of whatever value the fact may be, it 

 yet remains that no modern coral has precisely the same septal 

 sequence as is described for L. proUferum, which suggests that 

 here we have merely a specialized type of the Zaphrentoid coral. 

 Starting with the hypothesis that the primary septal plan of L. 

 proliferum is hexameral, we have yet to investigate other corals, 

 selected with the purpose of getting a primitive species as well 

 as one which is favorable for study, to find out how far they 

 lend support to the hexameral primary septal plan or tend to 

 disprove it. 



The difficulty involved in getting sections of coral tips that 

 really show anything one way or the other is appreciated only 

 after one has made the attempt. The tips either break at an 

 inopportune moment, or after sectioning show nothing con- 

 clusive. Turning from sections which revealed little or noth- 

 ing, I was more fortunate in securing some specimens of 

 Strejptelasma jprofundum from the Black River limestone. 

 The specimens were silicified and had been removed from their 

 matrix by acid. Though small, they showed the well-preserved 

 septa on the inside of the corallum. These specimens were 

 carefully examined. Two were found which revealed the 

 arrangement of the septa at the base of the calyx on the inside 

 of the coral so satisfactorily that they were set aside for 

 detailed study. During the attempt to sketch the relations of 

 the septa in one of these specimens the corallum was unfor- 

 tunately broken into several pieces so that it was impossible to 

 make a satisfactory drawing. A drawing of the other is given 

 in figure 16, which in all essentials is like the one which was 

 broken. 



