OF ARTS AND SCIENCES. 19 



from a small base, similar in size, obscurely heptagonal ; at the termina- 

 tions of the diameter opposite from the one which makes the suture 

 line they are prolonged into quite acute angles, forming the two 

 obscure angles of the heptagon. Immediately above the columnar 

 pit, or a very little below it, is a series of massive tubercles irregularly 

 disposed, and varying in size, the remainder of the bases being com- 

 paratively smooth. From the margin of the columnar pit extend, in 

 the direction of the arms, four raised folds, two on each piece, orna- 

 mented by several tubercles and strijB. 



Radials. The first are very large, pentagonal, trapezoidal in shape, 

 their upper facets being much wider than the lower ones. They 

 extend out as far as the first or second pieces beyond the axillary 

 radials ; the middle portions are swollen out into folds or plaits ; their 

 junction with the second radials is distinguished by a large tuberous 

 knob, beneath which are one or two smaller ones. A number of 

 striaj regularly disposed, and a few minute granules are scattered over 

 the surface of the pieces. This raised median line of the radial pieces 

 produces broad intervalla between each two of them. The second 

 and third radial pieces are very minute ; the second join the first 

 radials at the knobby prominence described above ; the third are 

 axillary, and give off two rays each. 



Inter-radials. One large inter-radial is placed between each pair 

 of arms. 



Ajial piece. At one termination of the articulating facet of the 

 basal piece (the other being at the anterior radial piece) is situated 

 a single anal piece. It is not so wide as the radials, but of the same 

 length, pentagonal ; as in the radials, its centre is elevated, it differs 

 from them in the portion where the second radials join the first ; on 

 the radials there is a well-defined, articulating facet, whilst on the 

 anal piece none exists, the piece being solid and continuous throughout. 

 Vault. We have no specimen showing the vault ; in one example 

 before us, there is a proboscis much crushed and misshapen ; it is large, 

 composed of many small, coarse, tubercular pieces, and extends not 

 quite one third the length of the arms. Its terminal point is appar- 

 ently formed by two circles of pieces surrounding a single one. 



Arms. From each third radial come off two arms. They are 

 about three times as long as the body, and arranged as follows : in 

 each arm six quite stout quadrangular pieces, rounded on the dorsal 

 surface, are superimposed upon each other; the sixth are axiUary, 



