110 WTNCHELL AND MARCY ON FOSSILS FROM THE 



Megistocrinus necis W. and M. 

 Plate II. figure 6. 



Body of medium size, pentaugularly ovoid, tapering below and contracted toward the 

 bases of the arms, giving the greatest diameter a little above the middle ; flattened along 

 the interradial spaces, causing the rays to occupy five conspicuous angles. The inter- 

 brachial spaces are also flattened. Basals rather small, hexagonal. First radials the 

 largest plates of the body, hexagonal or heptagonal, one third higher than wide, the lower 

 lateral sides much the longest. Second radials smaller, hexagonal, similar in form to the 

 first radials ; third radials heptagonal, in some specimens nearly twice as long as wide, 

 supporting on its two short upper sides a pair of hexagonal supraradials, above each of 

 which is a second. Regular interradials about ten ; the first a little smaller than the first 

 radial, hexagonal, approximately equilateral, surmounted by a pair of smaller plates, and 

 these by a pair still smaller, the others diminishing similarly in size upwards. First azyo-os 

 interradial heptagonal, a little smaller than the anterolateral first radials, supporting three 

 variable plates in the second series, of which the middle one is much the smallest. The 

 remaining ones gradually smaller, amounting apparently to twenty or more in number. 



The forms and arrangement of the plates in this species are quite similar to those of M. 

 Chridyi Hall sp. The bifurcation of the rays, however, is considerably lower. The form 

 of the cup, moreover, is very different, being somewhat obpyramidal below, instead of 

 urn-shaped, while it is also much contracted above. The angulations along the rays modify 

 the form of the cup, and are not to be compared with the small threadlike ridges occupy- 

 ing the same position in the Waldron species. The specimens show constant characters. 



Megistocrinus infelix W. and M. 



Plate II. figure 7. 



Body of moderate size, urn-shaped, having a rounded base, but slightly diverging sides, 

 and no constriction below the arm bases, which are somewhat prominent. Raised ridges 

 extend from the basals over the radials, supraradials, and brachials. Basals rather small, as 

 large as the second radials. Radials rapidly decreasing in size ; first radials large, nearly 

 as broad as long, with the upper side the shortest ; second radials with the upper and lower 

 sides short ; third radials oval, heptagonal. First supraradials regularly hexagonal, two 

 thirds as large as the third radials ; second supraradials similar in form, but smaller. 

 Brachials two beneath each arm-base. Arms in ten pairs. Regular interradials about 

 ten or twelve in each interradius; the first, hexagonal, as large as the second radials 

 or larger ; above this are two others of the size of the third radials, followed by about 

 three or four pairs decreasing in size. Azygos interradials apparently thirty or more, gen- 

 erally hexagonal in form, with nearly equal sides. 



Dome depressed, nearly flat, composed of a large number of plates, with apparently a 

 central proboscis. The dome is marked by ten radiating furrows, increasing in depth and 

 width from the centre to the spaces between the pairs of arms, and extending a short 

 distance down the side of the cup, where they vanish. The azygos furrow is much deeper, 

 and deeply indents the upper part of the azygos side of the cup. 



