PAL^ONTOLOG V. 



77 



HALYSITES CATENULATA, Linn. 



Synon., Halysites esharoides. 

 Catenipora labyrinthica, Goldfuss, etc. 



A great variety of forms of the chain coral are found which in gen- 

 eral structure are perfectly alike, but differ widely in the size of the 

 tubes, in the shape of the orifices, and in the mode of reticulated 

 connection between the catenate laminae. Some specimens have 

 elongate, lanceolate orifices, in others the form is oval, and in 

 others still nearly circular. In those with large elliptical orifices 

 the longer diameter is often fiv^e millimeters, and the shorter in the 

 transverse direction three millimeters ; in others the proportions 

 of the diameters of the orifices are two and a half millimeters by 

 two millimeters. In the smallest built specimens they measure one 

 millimeter only in the long direction, and one half in the shorter. 

 The loops of the laminae are in some forms narrow, in one direction 

 nearly as wide as in the other ; in other specimens the loops are 

 large, or the flexuose laminre may for long distances run in close 

 proximity, parallel with each other, before they make occasional 

 connection by short transverse branches. The contrast between 

 these various forms is very great, and it is evident that various 

 specific forms exist ; but while attempting to define them, I found 

 so endless a series of transitory connecting forms that I desist from 

 making a distinction, and use here the collective name of H. cate- 

 nulata for all. Found in the Niagara group of Michigan, as one of 

 the most widely distributed characteristic fossils ; likewise common 

 in the Niagara group of other States east and west. The first speci- 

 mens of the chain coral are found in the upper beds of the Hudson 

 River group, in the west portion of the Upper Peninsula of Michi- 

 gan, but their preservation is so imperfect that it is impossible to 

 determine whether these oldest specimens represent another species 

 or not. 



Plate XXIX, — Figs, i, 2 and 4 represent three of the many varie- 

 ties in which the coral is found associated in the strata of Drum- 



