126 Mr. H. M. Bernard on the 



become stout solid trabeculae. The rest of the reticulum 

 merely forms the cross pieces which support these trabeculee. 

 Every stage in the gradual differentiation of these trabecular 

 can be traced. In many cases the more vertical elements of 

 the thickening reticulum run in nearly straight lines, but 

 without thickening. Comparison of specimens shows that 

 the thickening was due to the rising up of the tips of these 

 vertical threads above the surface, perhaps at first as echinulse. 

 These became stouter and stronger, probably for protective 

 purposes, and thus, as they sank beneath the rising surface, 

 became thick trabeculaj (fig. 3 c). 



This group, showing the rising of stout trabecule above 

 the surface to form protective " tubercles," is very large and 

 contains more than forty types. The distribution and shapes 

 of the tubercles are very varied : they may be densely 

 crowded as minute rounded granules or tall and lancet- 

 shaped ; they may be grouped in rings round calicles, or, 

 again, they may run together to form thin keels or ridges. 

 This group is called the " tuberculate " group. 



We thus have four main divisions of the genus — glabrous, 

 foveolate, papillate, and tuberculate — each term having refer- 

 ence solely to a peculiar specialization of the coenenchyma. 

 While the first three of these terms need no comment, the 

 last requires justification. 



In all the earlier descriptions of Montiporan types the terms 

 papilla and tubercle seem to have been used indiscriminately. 

 It is often impossible to tell whether a writer was describing a 

 specimen belonging to group 3 or to group 4. The most 

 important use of the word tubercle occurs in Lamarck's 

 description of the specimen Pontes tuberculosa, Lk. {=:Afonti- 

 pora tuberculosa). In fixing the use of the word tubercles to 

 mean the small solid tips of individual trabeculse when they 

 project above the surface, I have been led to do so by the 

 conviction that these were Lamarck's " tubercles " as seen on 

 his type " tuberculosa^ Certain expressions in Lamarck's 

 text point clearly to this. In describing P. tuberculosa * he 

 speaks of " les tubercules dont la surface est parsemee " as 

 being " graniformes ou columniformes ; " and, again, on the 

 next page he speaks of interstices being " heriss^s de tuber- 

 cules." Both these expressions are quite inapplicable to the 

 much larger swollen reticular knobs here called papilla. 



One other remark on these tubercles witii their trabecula- 

 like sunken portions. It was the presence of these trabeculee 

 which appears to have misled Milne-Edwards. He compared 



* * Aniuiaux saus Vertebres,' ii. 1816, p. 272. 



