On a new Order of Echinodertns. S7\ 



In some well-preserved examples, I have seen on the sides of 

 the lobes, near to the articulation, fine and close oblique strise, 

 apparently indicating muscular attachments, and which, judging 

 from their position, gave attachment to large muscles moving 

 the rays, and rendering it improbable that they were thrown off 

 as by the Brittle-stars. The fact of finding no young specimens 

 would also support this view. 



In describing the ornamentation, the different parts will be 

 spoken of as regions j they will be the anterior, the dorsal, and 

 right and left lateral. 



Some remarks may now be made on the value of the group, 

 and on its position in the Echinodermatous class. The general 

 form of the creature has already been shown, with great proba- 

 bility, to have been pentalobular, so that it must have greatly 

 resembled such a star-fish as a short-legged Ophidiaster. Now, 

 the question to be determined is — are these fossils most closely 

 related to the Asteroidea or Ophiuroidea ? and also to see in 

 what respects they differ from them. Unfortunately, almost the 

 only structure that can be compared is the visceral groove. A 

 remarkable feature about it, which will at once attract notice, is 

 its relative smallness to the whole size of the ray; while, if the 

 ventral covering of a star-fish were removed, the visceral cavity 

 would be seen to be coextensive with it. The rays of Brittle- 

 stars are very slender, however, and the internal cavities, in 

 proportion to the size of the disk, very small. The cause of 

 this difference in size is well known : there are in Brittle-stars 

 no csecal appendages to the stomach ; and the ovaries being in- 

 cluded within the disk, there is no necessity for the space which 

 these bulky organs require. Hence, as the groove contains no 

 space but such as would be required for accommodating the 

 ambulatory organs, we shall be justified in supposing that the 

 ovaries were included within the disk ; and it will be very pro- 

 bable that there were no csecal appendages. Thus the fossils 

 are clearly to be excluded from the Asteroidea. There is, how- 

 ever, another argument for their exclusion, in the solidification 

 of the rays : this alone could not be considered more than a 

 generic difference, except that in a star-fish it would be only 

 reasonable to suppose that all parts would be solidified alike, so 

 that the suckers should have been protruded through pores in 

 a solid plate ; this would have indicated a transition to the 

 Echinoidea, constituting at least a new suborder. 



The whole sum of the characters is so entirely different, that 

 they may with equal certainty be excluded from the Ophiu- 

 roidea. 



Nor is it possible to suppose any relationship with the Echinoi- 

 dea, since those forms to which they make the nearest approach 



