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TRANSACTIONS OF THE 



We will first communicate the results of our observa- 

 tions upon the fossil itself, and point out in what parti- 

 culars it differs from those published by naturalists. Mr 

 Say (see Journal of A. N. S,, vol. 4, page 292) says that 

 the aperture in the summit, where the ambulacra join, 

 is angular; and Dr Goklfuss (Goldf., Petrefacta, page 

 160) says that it is pentagonal. Such is the fact, the 

 form of this aperture varies much according to the more 

 or less perfect state of the fossil, but in perfect indivi- 

 duals its form is a star with five rays. 



Dr Goldf uss speaks of an arrangement of pores on the 

 ambulacra which I cannot see on our specimens, and I 

 have anatomised some in order to detect it. The doctor 

 says (loco citato) : " they" (ambulacrorum arese) " are 

 divided by a smooth longitudinal furrow, transversely, 

 narrowly striated, and their tentacula have pores which 

 are placed in pairs. These pores are close to one 

 another, the outer row immediately on the border of the 

 area, indeed in the very identical furrow itself, but the 

 inner one is on the extremities of these transverse strise 

 of the ambulacra themselves ; at the first glance, the 

 large pores of the external row are only perceptible, and 

 those of the inner row are so small that they can be seen 

 only by a magnifying glass." We examined several 

 specimens and, as already mentioned, we dissected some 

 also (we have some in our cabinet, the different parts of 

 w^hich may be separated), and we have not been able to 

 discover this arrangement of pores. The pores placed 

 at the end of the transverse striae, which Dr G. says are 

 very small, do not exist ; but the large ones placed in the 

 furrow formed by the ambulacrum, and the margin of 

 the continuation of the pelvis or scapula, are very per- 

 ceptible. When the ambulacrum is removed, the whole 

 mystery of these pores is cleared up ; we then see that 

 each of these transverse strisB terminates in the form of an 

 arrow head, and joins with its point the border of the 



