A MONOGRAPH OF THE EXISTING CRINOIDS 35 



NOTOCRINIDAE 



Notocrinus virilis. — In a specimen with the arms 75+ (probably about 125) mm. 

 long the third brachial has 18 septa, 3 or 4 finished and only 2 incomplete; the degree 

 of strength is 2. The areola is narrow, but there appears outside of this a very broad 

 almost smooth area occupying about half the space between the lumen and the 

 margin of the ossicle. Beyond this area there is a stout concentric synapticula, and 

 beyond this a similar weaker one. In another case there were 19 septa, about 4 

 incomplete. Two eighth brachials had 19 and 20 septa and 2-3 weak synapticulae ; 

 the degree of strength is 1 . 



Antedonidae 



Antedon petasus; — In a specimen with arms about SO mm. long the third brachial 

 has 21 septa, 12 complete, and an indistinct areola; the degree of strength is 2-3. 

 In another case there are 19 septa. The ninth brachial has 19 septa with an abnor- 

 mally large and stout areola. The fifteenth brachial has 19 septa. The nineteenth 

 brachial has 19 septa, of which 12 are complete, and a narrow distinct areola. In 

 the last two hypozygals there is a distinct ventral beam. 



Compsometra serrata.- — In a specimen with an arm length of 30 mm. the third 

 brachial has 14 septa, 9 complete, and a narrow areola; the degree of strength is 2. 

 In another case there are 12 septa, about 10 complete. The ninth brachial has 13 

 septa, including 2 indistinct ventral beams. The fourteenth brachial (third hypozygal) 

 has 14 septa. 



Isometra vivipara. — In a specimen with arms 60 mm. long the third brachial has 

 14 septa, 10 complete; most of the septa are finished about halfway to the border of 

 the ossicle; the areola is narrow; the degree of strength is 2. From the fourth or 

 fifth syzygy onward septa are lacking, the union becoming a loose synostosis, with 

 about the lumen a rather marked areola situated in the center of a somewhat con- 

 cave face. 



Heliometra glacialis. — In a specimen with an arm length of about 200 mm. the 

 distal face of the third brachial has about 36 septa; there are 22 complete septa, 

 about 6 ventral rows of tubercles, and 2-3 concentric synapticulae, of which the 

 innermost is the stoutest; the areola is dorsally rather moderate, ventrally very 

 broad ; the degree of strength is 4. In two other cases there are 39 septa, 22 complete, 

 6 rows of tubercles, and 2 ventral beams. The twenty-sixth brachial (sixth hypo- 

 zygal) has 29 septa, including two ventral rows of tubercles; the septa are somewhat 

 lower than those on the third brachial, and the areola is narrow. 



Promachocrinus kerguelensis.- — In a specimen with arms about 150 mm. long the 

 third brachial has 27 septa, 11 of these incomplete, and on each side of the median 

 line 3-5 ventral tubercle rows; the degree of strength is 4. In another case there are 

 30 septa including 8 rows of tubercles; the areola is narrow or of medium width, 

 indistinct, sometimes lacking. The ninth brachial has 32 septa. The fourteenth 

 brachial (third hypozygal) has 34 septa, including 7 ventral rows of tubercles; more- 

 over, many of the septa are partly subdivided into rows of tubercles. 



Leptometra celtica. — In a specimen with an arm length of about 70 mm. the third 

 brachial has 24 septa, about 12 complete septa, 3 of these finished, and 2 ventral beams; 

 the areola is narrow and indistinct; the degree of strength is 2. In another case 



