EARLV DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 221 



but their dismembered skeletons have been scattered broadcast and the 

 extraordinary accumulation of this debris is an index of the great profusion 

 of these interesting forms of sponge life in the seas of the time. 



The spicules of the Hexactinellida have been extensively described by 

 various authors, Thomson, Schulze, Sollas, Rauff, Hinde, the writer and 

 others and a somewhat bewildering nomenclature has been adapted to their 

 various expressions. We present in the following the series of these varia- 

 tions so far as observed, and some of these may prove of special interest to 

 students of the morphology of these bodies. 



1 A normal smooth hexactin (^x;/-or liohexactiii) frequently with the 

 arms of one axis longer than the rest. Occasionally these smooth arms are 

 somewhat irregularly curved [fig. 17, 18, 21, 23, 24]. 



2 EcJiiuJicxactins or hexactins with thorny protuberances on the arms. 

 These are considerably varied in size and form, some being slender with the 

 asperities low and far apart but the commoner are large stout hexactins with 

 the spines arranged in distinct spirals about the shaft of the arms. This is 

 a very singular structure which so far as I know has not been observed 

 before but is a very pronounced and common type [fig. 22, 25]. 



3 Hexaster. Hexactins with branches on the rays, generally four on 

 each but sometimes three on one or more, are found and in these the axial 

 shaft is continued beyond the single circlet of branches. It is very simi- 

 lar to a spicule figured by the writer from the Lower Carbonic, G r i p h o d- 

 i c t y a e p i p h a n e s H. & C' 



Most remarkable in this series of spicules are the ancistroid shapes 

 presented quite abundantly in the material at hand with a variety of expres- 

 sions. In several of these the triaxial origin is safely indicated though the 

 development is essentially a single rod with terminal modifications usually 

 at one end only. The simplest of all these hooks and one of the rarer expres- 

 sions is such as is shown in figure 6 in which the shaft seems not to have 

 been long but the recurve is deep and narrow. We have no evidence as to 

 whether the other axes were represented in this form. The commonest of 

 all these hooked spicules are those in which the recurved end is divided into 

 two branches partaking of the curvature of the hook though they vary in 

 degree of curvature and in the angle which they made with the axis. 

 Sometimes the shaft in these is short and tapers to a point without evidence 

 of the other axes, but usually the end opposite the grappling hook has a 

 pronounced development of the axis shown in four curved horns spreading 

 out and up, slightly knobbed or hooked at the ends ; from within these, like 

 the pistil of a flower, rises the short knob representing the extension of the 

 main axis. This singular combination of hooks at one end with regular 

 curved branches at the other is a type which evinces notable and even 



■ N. Y. State Museum Mem. 2, 1898. The Paleozoic Reticulate Sponges, p. 180. 



