MONOGRAPH OF THE EXISTING CRINOIDS. 569 



A third has the five primitive cirri still more developed and composed of 9 

 or 10 segments. Between two of these cirri and immediately above them there is a 

 sixth filiform cirrus directed upward which has no distinct articular divisions and 

 terminates in a simple conical tip, the claw not having as yet developed. This 

 cirrus, which has appeared later than the others, is interradial ; the first five always 

 maintain their original radial position. 



The fully developed pentacrinoid stage is represented by seven specimens. Of 

 these, six were taken in March, April, and the beginning of May at Skraaven and 

 at the Guldbrand Islands at the depths already given. They were attached to the 

 tests of different rhizopods, to small shells, etc. The seventh is that taken by 

 Professor Sars himself, in the middle of March, at Manger, near Bergen, in 50 

 fathoms, which he described in 1856. 



The largest complete specimen was attached to a Crisia dcnticulata. It 

 measures 28 mm. in total length, the crown (with the arms) being 8 mm. long. 

 The column is composed of 44 segments, which seem generally shorter than in the 

 preceding stages (the longest are almost four times as long as broad), having in- 

 creased considerably in thickness. 



The three proximal columnals are almost discoidal, separated from each other 

 by straight and deep constrictions, and are peculiar in that their surface shows 

 moderately large transverse grooves, irregular, and somewhat sinuous, as if they 

 were composed of thin transverse lamellae. Professor Sars believes that the loose 

 structure of these segments has to do with the detachment of the pectacrinoid from 

 the column. 



In the individual in question the two topmost columnals are the most discoidal. 

 being two or three times as broad as long; the third is a little less broad and the 

 fourth narrows a little toward its lower end, which is not broader than the following 

 segments, which, as usual, are cylindrical and progressively increase in length. 



All the elongated columnals show very distinctly (a fact which was difficult 

 to appreciate in the preceding stages on account of the smallness of the object) 

 the same structure as the columnals of fihisocrinu^. The two thickened ends are 

 somewhat compressed laterally, so that the articular faces are more or less elliptical. 

 On the two faces of each columnal this compression takes a direction almost at 

 right angles, so that the longer axis of the ellipse on the distal end crosses that of 

 the ellipse on the proximal end at an oblique angle. The compression alternates 

 at succeeding articulations all along the column. 



The articular faces show two similar large rounded fossae, one on either side 

 of the longer axis. These fossae are united in the middle by the circular axial 

 canal. The fulcral ridge, interrupted in the middle by the central canal, shows 

 about six very small conical teeth on either side. The fossae contain a large number 

 of soft parallel fibrillae, very fine and strong. 



Additional cirri have appeared on the centroclorsal, so that there are now nine 

 larger and five smaller. The longer are well developed and are composed of 10 

 segments, of which the distalmost, as in the free adults, is already furnished with 

 two claws. The five smaller cirri, situated immediately above and between the 



