MONOGRAPH OF THE EXISTING CRINOIDS. 563 



Total length (distal portion of column missing), 3.0 mm.; length of calyx, 

 about 0.8 mm. 



The stem fragment attached to the calyx consists of 12 columnals, of which 

 the first four are very short and discoidal, the fifth 'is half again as long as 

 broad, the sixth is twice as long as broad, and the tenth and following are about 

 five times as long as broad. 



The radials are rhombic plates of moderate size. 



HATHROMETRA TENELLA. 



A pentacrinoid of this species was figured by Verrill, who, however, gave 

 no description of it, nor did he indicate where or at what depth it was dredged. 



The figure shows a specimen 22.5 mm. in length, the crown being 4 mm. long. 



There are 28 columnals, of which the topmost six are very short and dis- 

 coidal, decreasing slightly in diameter. Those in the distal half of the column 

 are shown as five or six times as long as broad, with slightly enlarged ends. 

 Though the object of attachment is drawn, no terminal stem plate is shown, and 

 many of the earlier elongated columnals are drawn as two, the median annulus 

 having been mistaken for the border between two. 



The distance across the distal part of the radial circlet is equal to about 

 twice the distance between the distal portion of the radial circlet and the topmost 

 columnal. The sides of the calyx are rather strongly convex. 



The radials in the middle line are about as long as the interbasal sutures. 

 The distal edge of the radial circlet as seen in lateral view is straight. 



The bases of the IBr 1 occupy about half of the distal edge of the radials. 



Nine brachials are shown. No pinnules are developed. 



On September 12, 1884, the Albatross dredged a nearly or quite fully grown 

 pentacrinoid off Cape Hatteras in 243 fathoms. 



The total length is about 17 mm., the crown measuring about 6 mm. 



There are 29 columnals and the terminal stem plate and centrodorsal. 



The centrodorsal is apparently a low truncated cone; the columnal imme- 

 diately following the centrodorsal is very thin and platelike, rather strongly 

 pentalobate, the interradial portions being produced laterally as broadly rounded 

 extensions, suggesting the conditions found in Promachocrinus ; the next seg- 

 ment is less in diameter, slightly thicker, the proximal border produced and 

 rounded pentagonal with the angles interradial, the sides converging strongly 

 distally. These two columnals are very closely united, apparently by a stem 

 syzygy. The following columnal is less in diameter than the preceding and 

 longer, being four or five times as broad as long, united both to the preceding 

 and to the succeeding by the bourgueticrinoid type of articulation. The fourth 

 columnal from the centrodorsal decreases rapidly in diameter distally, and is 

 about as long as its distal breadth, with a roughened girdle about the proximal 

 border. The fifth is about twice as long as broad, with a roughened, very slightly 

 raised, broad median girdle. The following increase in length to the eighth, 

 which, with the following, is about three times as long as broad. After the 



