132 LOWER PENINSULA. 



crossed by the carinae. On the expanded marginal portion of the 

 calyces the plications lose their crest form and are reduced to 

 rounded ruga:, which, through division or through the implantation 

 of new ones between them, multiply to three or four times their 

 original number, and have then the form of equal, narrow, linear 

 stripes. On both sides of each of these stripes a row of circular 

 pores opens with closely crowded orifices alternating in position 

 on the opposite sides. In some specimens the inner cell pits are 

 surrounded by a monticulose raised rim ; in others the surface of 

 the calyces is roughened by blisters without a distinct radial stria- 

 tion ; these conditions represent the different stages in the growth 

 of the coral which it undergoes previous to the deposition of a new 

 well-finished calycinal floor. The great difference in the size of 

 the calyces of some specimens has induced D'Orbigny to dis- 

 tinguish the larger-celled form, as Stroinbodes striatiis, from the 

 smaller-celled Stroinbodes pcntagoiius of Goldfuss, but it is impossible 

 to draw a dividing line between them ; all gradations of sizes, from 

 the large to the small forms, can be found associated in the 

 same localities, and in structure not the least difference exists be- 

 tween them. 



Occurs very abundantly in the Niagara group of Point Detour, 

 Drummond's Island, etc., and frequently found in the drift. 



Plate XLVIII. — Fig. i is a silicified specimen corresponding with 

 Strombodes striatus, D'Orbigny. Fig. 2 represents the typical form 

 of Goldfuss's species, Strombodes pentagonus. 



The Niagara group of Kentucky and Indiana incloses an abun- 

 dance of specimens, which appear to be in every respect identical 

 with the above-described species, but I observe that the interstitial 

 layers of vesicles in the specimens from Michigan are always of 

 much coarser structure than in the specimens found at Louisville, 

 etc. 



STROMBODES PYGMyEUS, N. Sp. 



Calyces not defined, composing laminar surfaces dotted with 

 abrupt cell pits, about two millimeters in width, and distant from 

 each other six or eight millimeters. The broad interstitial surface 

 is striate by the diverging radial rugae of the cell cups, which meet 



