32 1'ALiEOXTOLOGY 



Encrinite" (Marsupites, fig, G, 9), is found only in the chalk, 

 along with Bourgvbetierinns (fig. 7, 10) ; and the bodies of Co- 

 matulm, which, when they have lost their arms and claspers, 

 are called " Glenotremites." (Fig. 7, 7, — upper surface with 

 sockets of the five arms ; 8, — under surface, shoving articula- 

 tions of claspers, and the scar of the larval stem.) 



Order 2. — Cystoidea. 



This order was established by Von Buch for a small group 

 of palaeozoic echinoderms formerly included with the Cri- 

 noidcw. They have a globular body covered with close-fitting 

 polygonal plates attached by a simple jointed stem. The 

 mouth is minute, and opposite to the stalk ; close to it is the 

 small anal opening ; and a little more distant the generative 

 orifice, covered by a pyramid of five or six little valves. Some 

 of the genera, like Pseudocrinus (fig. 6, 2), have two or four 

 tentaculiferous arms, bent down over the body and lodged in 

 grooves, to which they are anchylosed. Others, like the 

 S]jhwronites (fig. 6, 1), have only obscure indications of ten- 

 tacles situated close to the mouth. In Pseudocrinus and some 

 other genera two or three pairs of lamellated organs, called 

 pectinated rhombs, are placed on the contiguous margins of 

 certain body-plates. They are supposed not to penetrate the 

 interior, and no office has been conjecturally assigned to them ; 

 but Professor Forbes suggested that they might represent the 

 " epaulettes" of the larval Echinida\ to which group he sup- 

 posed the Cystidean bore the same relation as the Crinoids 

 hold to the star-fishes. There are nine genera, of which eight 

 are found in the British strata — four in the upper and four in 

 the lower Silurian. 



