234 PROCEEDINGS OF THE ACADEMY OF [18*79. 



of certain pores or openings located between the arm bases and 

 separated from the arm passages by a thin partition. Their num- 

 ber varies from ten to twenty or more. In Batocrinus, where 

 they are most conspicuous, there are twenty, no matter whether 

 the species has more or less than twenty arms. They are about 

 one-third the size of the arm passages, with which tliey are in 

 very near the same horizontal plane. There are two pores to 

 each interradial field, one to the left of one arm, and one to the 

 right of another. Ten other pores have a radial position, two 

 within each of the five axillary spaces which form the median 

 portion of the rays. In Strotocrinus, which has an enormous 

 body, each arm has a pore, and so in Steganocrinus, Eucladocri- 

 nas, and apparently in all genera in which the arms branch off 

 alternately. Other genera have only ten pores. In Ollacrinus 

 the pores are represented by two longitudinal passages through 

 the tubular extensions of the interradial series, or the false arms 

 as usually called. 



As these openings, especial^ in Batocrimis, are comparatively 

 large, it is somewhat surprising that they have never been men- 

 tioned by other paleontologists. Their position corresponds almost 

 exactly with that of the so-called ovarian apertures of the Blas- 

 toids though they are placed at a greater distance from the radial 

 centre. The openings in both groups are situated within the 

 brachial zone or at the extreme border of the summit. In the 

 Blastoids the ventral disc or summit is reduced to the minimum 

 in size, being composed only of the covering of the ventral open- 

 ing ; and this explains why the orifices are here found close to the 

 radial centre, while in the forms above named they are located 

 away from it. The pseudambulacral fields of the Blastoids repre- 

 sent the ventral groove of a recumbent arm, and the small pas- 

 sages which enter the body near the apex and beneath the central 

 covering are the homologues of the arm passages in the true 

 Crinoids. (Compare PI. 17, Fig. 4.) The so-called ovarian open- 

 ings are therefore located beside the arms, just as the pores in Bato- 

 crinus, and this strongly indicates a similarity in their functions. 



In addition to this the perivisceral cavity in the Actinocrinid.se 

 contains a number of chambers, and, from the brachial zone down 

 to the base, is separated from the visceral cavity by a peculiar 

 partition or network, pierced by innumerable pores and passages 

 leading toward the visceral cavity which contains the digestive 



