PLATVCRINID^. PLATYCRINITES. 



The P. l(cvis appears to be more abundant in the lower and middle beds of the 

 carboniferous limestone, than in the upper. 



Description or the Calcareous Frame Work. 



The DORSO-CENTRAL PLATE, ( Pelvis of MUUr), PI. \. fig. 1. n, is convex externally, 

 with the angles of the pentagon, which it forms, tm-ned upwards, so that its figure 

 becomes somewhat circular when viewed in connection vdth the plates which it sup- 

 ports. Externally, in the centre, is a circular depression finely striated in radii, for the 

 attachment of the column. A central perforation preserves the communication between 

 the column and body of the animal. 



The Perisomic plates, (Scapuhe, Miller), PI. \.fig. 1. i, h, are five in number, which 

 adhere to each other by theii* lateral edges. Their lower edges are somewhat orbicular, 

 and their whole contour rounded, so that the perfect animal, instead of presenting a 

 conspicuous pentagonal appearance, as stated by Miller, is only slightly of that figure. 



Abdoiniinal plates. — The integument which extended over the abdominal cavity was 

 strengthened and protected by numerous smooth, chiefly hexagonal, plates, fi-om which 

 proceeds the elongated proboscis, which is also covered -with smooth plates of similar 

 form. 



Proboscis. — The figiu'es 1. and 2. e, /, j>, and q, PL 1. are liighly interesting, as bemg 

 faithful representations of that singular organ, the proboscis or oral tube, and which has 

 never been noticed by previous observers as appertaining to this species. In some 

 specimens the proboscis is frilly two inches and a half in length, and rises fi-om the 

 centre of the plates covering the \dscera. It is protected by continued series of smooth 

 hexagonal plates fi'om its base to the apex, where it is completely closed m mth a few 

 iiTegular shaped ones, so that the mouth must have been valvate. The oral tube pos- 

 sessed sufficient flexibility to have enabled the animal to move it in every direction, so 

 that it was admirably adapted to take up any object, however minute, which the tenta- 

 cula might have captured, and which was proper for the sustenance of the animal. 



Rays, or Arms. — The five mam rays, or arms as they have been frequently termed, 

 are each composed of a single cunieform joint. PI. \. fig. 1. h. On the outer faces of 

 this joint the two secondary rays (hands) articulate, each of these consists of two joints, 

 the upper of which is cunieform. PI. \.fig. \. g. h. From each of these upper jomts of 

 the secondary rays proceed two lesser rays, (PI. I. fig. 1. «, e, g, h.) which are composed 



