224 



PALEONTOLOGY OF NEW-YOEK. 



Fig. 1 A. A small specimen with several of the arms still remaining attached. 



Fig. 1 i. A fragment of slate enclosing the arms of a large individual, several of which are 

 shown in the figure, in a broken and distorted condition. 



Fig. 1 ^. A portion of a single arm or finger, natural size, showing it to be composed of a double 

 series of joints ; a thin lamina of each penetrating deeply between the two adjacent 

 ones, and interlocking them strongly together. Each joint is marked by an elongated 

 tubercle in the middle, and a shorter one at each side as shown in fig. 1 I. 



Fig. 1 m. A fragment showing the inner margin with the tentacula attached, in alternation with 

 the joints of the fingers. The tentacula are apparently composed of a double series 

 of joints alternating with each other, or of joints having a peculiar shape, and longitu- 

 dinally marked by a deep groove. These are so minute in the original, that it is 

 difficult to decide positively in relation to this character. 



Fig. 1 n. A large separate plate, showing the arrangement of rows of pores, and surface marking 

 of the ordinary character. 



Fig. 1 0. A plate where the radiating ridges are developed between and by the side of the rows 

 of pores, with scattered tubercles over the remainder of the surface. 



Fig. 1 p. A similar plate where the ridges and tubercles are more strongly developed. 



Fig. 1 r. An enlargement of several of the little pustular elevations, terminated above by the 

 opening of the pore. 



Fig. 1 11+. A portion of a pelvic plate highly magnified, showing the vesicular tubercles in place 

 of the pores. 



Fig. 1 o + . A portion of a scapular plate highly magnified, showing the pores with two, three 

 and more apertures, opening like little vesicles upon the surface of a tubercle 

 scarcely raised above the surface of the plate. The number of vesicles increases from 

 the base of the plate, to the termination of the rows in the centre. 



Fig. 1 e*. The interior of a scapular plate, showing that the apertures of the pores are simple, 

 as in the other plates, though opening in numerous minute perforations at the centre. 



Fig. 1 p-\-. Parts of other scapular plates, showing the vesicular tubercles, and the same where 

 they have increased in size and coalesced, forming a continuous ridge, as in many 

 of the larger or full grown individuals. 



Fig. 1 s. The inside of one of the hexagonal plates, showing the openings of the pores on the 

 inner side, and the grooves extending from them to the margins of the plates. In 

 this plate there are no pores sending tentacula to the lateral margins ; the double 

 row from the centre to the upper and lower angles, sending grooves to the basal and 

 upper margins. The centre of the plate, including all the space between the rows of 

 pores, has become thickened, forming a broad callosity. 



Fig. 1 t. An enlargement of the preceding figure, showing more distinctly the character of these 

 little grooves, margined by a thin border, and a space between these and the border 

 of the next groove. 



Fig. 1 t + . The inner side of one of the heptagonal plates, showing the arrangement and di- 

 vergence of the grooves from the pores. A few pores occur near the lateral margins 

 of this plate, sending out grooves as described in the detailed description given of 

 their arrangement. 



