226 PROCEEDINGS OP THE ACADEMY OF [1881. 



both are placed between the sutures and appear as grooves situated 

 witliiu the upper series of radials. The grooves in the calyx are 

 opposed by similar grooves in the corresponding parts of the dome, 

 and pores as well as arm openings enter the body horizontally. 

 The grooves which constitute the arm openings follow the median 

 course, while the smaller grooves, forming the pores, enter ob- 

 liquely from the sides, and join the others at — or just before — the 

 point where they enter the general cavity of the body. The 

 pores which are given off toward the outer arms of the ray are 

 deeper than the rest, and connect with the arm openings at the 

 moment these enter the general cavit3\ Those of the inner arms 

 meet midway in the test, and in case there is another arm between 

 the two divisions of the ray, its pores join the arm passages close 

 to the outer surface of the test. This explains the fact that the 

 partition between the two last-mentioned openings is so rarely 

 preserved, and that these openings are generally found united in 

 the fossil. The arrangement of the pores is similar in other genera 

 of the Actinocrinidae, the pores between the main divisions of the 

 ray being universally more conspicuous than the inner ones. In 

 the Plat3'crinid£e and other genera in which the upper radials are 

 extended into free rays, the pores are located at the base of the 

 arms, not at the base of the free ray, and hence are rarely 

 observed. OUacrinus, so fer, is the only genus in, which, in con- 

 nection with the pores, appendages have been observed. They 

 there form heavy, arm-like extensions, often surpassing the arms 

 in length, with a channel through their centre. The channels 

 unite with the arm passages within the test in a similar manner as 

 the pores in Batocrinus. 



The affinities which are apparent between the pores of the 

 Actinocriuidaj and the ovarian openings of the Blastoids with 

 regard to their position, suggests a probable analogy in their 

 functions, and if the latter served as a madreporic apparatus it 

 would seem reasonable to suppose that tlie pores in the Actino- 

 crinidae did the same. But there are objections to this, and 

 another interpretation is at least possible. From what is now 

 known of the ontogeny of the Palteozoic crinoids, we are inclined 

 to think that the pores maj^ have been originallj^ pinnules, wliich 

 with progressing growth were soldered into the body. This would 

 explain the fj^ct that all pores located beside tlie inner arms are 

 located closer to the arm openings than those of the outer arms, 



