498 LONSDALE ON MIOCENE CORALS FROM N. AMERICA, 



of limited length. The finest specimen had a somewhat trape- 

 zoidal form, the greatest breadth being rather more than 6 inches, 

 the greatest width 4|-, and the greatest thickness 2. The opposite 

 surfaces were slightly uneven, but perfectly occupied by well-pre- 

 served mature stars, and the edges were slightly lobed or fractured. 

 The greatest range of the columns was about nine lines ; and the 

 width of the terminal stars almost uniformly two lines. 



In the lower portion of the most regularly formed tubes, 

 which might be considered as representing an early condition of 

 the coral, there were only twelve very thin slightly curved 

 lamellae, each formed, however, of two closely united plates, and 

 the arched or flat union of the opposite plates constituted the outer 

 wall. In the lower portion of tubes not regularly developed, the 

 lamellae varied in number, being for the greater part rudimentary, 

 as well as in form and mode of union ; but they were relatively 

 very thick, and their biplated composition was perfectly distinct : 

 the outer wall had also considerable dimensions ; and the trans- 

 verse laminae were greatly contorted. In this portion of both 

 regular and irregular tubes, the sides of the lamellae and of the 

 inner wall were vertical, and not minutely tuberculated ; and the 

 interspaces were deep and open. As the coral advanced towards 

 maturity, the number of lamellae increased to twenty -four, six of 

 which were simple and rather prominent, and ranged from the 

 periphery to the centre, while between each of these was a group 

 composed of two converging narrow plates with a middle broad 

 one, which extended also to the centre. In this state, the upper 

 edges of the lamellae and the boundary wall began to thicken, and 

 to be coated with fine papillae ; the interspaces were also con- 

 tracted, but the cup was relatively deep, with slightly tuberculated 

 edges. In what was believed to be the final state of growth, the 

 changes just noticed were much more marked ; the six simple 

 broad lamellae rose distinctly above the others, the papillated 

 layer extended across the interspaces, and had relatively con- 

 siderable thickness (two lines), the depth of the cup was greatly 

 diminished, the boundary of the stars had lost their tubercles, and 

 the separation was almost constantly defined by a well-marked 

 groove. In this state, no line of natural separation between the 

 columns could be detected, the thickening being apparently per- 

 sistent, and regularly developed, conforming to the structure of the 

 stars, the characters of which were uniformly exhibited. These 

 specimens, it should be remarked, indicated clearly that the polypes 

 died long previous to their solid fabrics having been enveloped in 

 mineral matter, fragments of small parasitic testacea being attached 

 to the surface, and the exterior as well as the interior being 

 penetrated vertically and obliquely by the vermiform cavities of 

 some existing species of marine animal. They exhibited also the 

 peculiar aspect displayed by existing Anthozoa, after the death of 

 the animal, over the whole or a portion of a specimen. 



Changes somewhat analogous, as respects the obliteration of the 

 terminal cup, occur in a polypidom belonging to the coral rag of 



