1879.] NATURAL SCIENCES OF PHILADELPHIA. 237 



in which no trace of them has as yet been discovered. These in- 

 clude among others the Ichthyocrinidse, and a few genera of the 

 Ar/fnocrinidse and Cyathocrinidae. In the Ichthyocrinidse, respi- 

 ration may have been carried on through the pliant vault, aided 

 by the expansions and contractions which the flexible nature of 

 the skeleton could produce. In the Actinocrinidse, however, the 

 body, as in the Blastoids, is perfectly rigid, the plates heavy and 

 firmty cemented together. There are no other openings in the 

 body but the anal aperture, the arm passages, a passage through 

 the column and the pores between the arm bases which we have 

 described. In some genera, however, the last-named pores appa- 

 rently do not exist. The introduction of water through the anal 

 tube need not be considered for a moment, nor through the arms, 

 which in no group of the Echinoderms perform such an office. Let 

 us examine the column. 



The construction of the column varies in different genera. It 

 is perforated throughout the centre by a passage connecting with 

 the interior of the body, which in some cases is a simple, small, 

 round opening, while in others it is very large and marked by a 

 peculiarly complicated internal structure. In the latter, the tubu- 

 lar cavity extends to all the branches which spring off rather 

 numerously toward the root. It is mostly pentamerous, though 

 in some cases tri- or quadri-partite ; it is sometimes regularly pen- 

 tagonal, and sometimes divided into five petaloid chambers which 

 unite at the centre. The walls within appear as if built up of thin 

 lamina?, with spaces between, sometimes pectinated, and variously 

 sculptured, all producing a great multiplication of exposed sur- 

 faces. In some the articulating faces of the stem segments are 

 covered with striae, radiating from the centre, which resemble 

 minute pores penetrating the walls. We have found the very base 

 of one of these large columns just as it was attached to the rock 

 or other flat surface. It is very broad and deeply channelled on 

 the bottom, and there are numerous branches or unattached cyrrhi, 

 all of which are perforated, and through which there was ample 

 communication with the surrounding water. In addition to this, 

 there are large pores near the base of the column, leading from with- 

 out into the main cavity directly through the walls. 



Such an extraordinary structure was not necessary, if the column 

 was merely an attachment or anchor for the Crinoid. That it was 

 a means of communication between the water outside and the in- 



