AUSTIN ON A NEW GENUS OF ECHINODERM, ETC. 44-7 



Altlioiigli present during tlie removal of hundreds of tons of lime- 

 stone, and diligently and repeatedly searching every bed and cranny 

 in the locality, I was unable to detect the least indication of a fourth 

 specimen. It may therefore be inferred that Protoechinus is of rare 

 occurrence ; and that v^hen the Hook limestone was accumulating at 

 the bottom of the Carboniferous sea, it had just appeared on the 

 stage of life among the then living echinoderms. 



As far as can be judged from the three specimens procured, I con- 

 sider it to be a true echinus, and in all probability the primitive form 

 of that now extensively diffused genus. Believing that Protoechinus 

 was one of the first, if not the very first true echinus, that appeared 

 on our globe, I have adopted the name as suggestive of that fact. 



Ohservations on the Genus PalcecMnus. 



From specimens of Paleechinus which I have in my cabinet, there 

 is great reason to infer that the different species belonging to that 

 genus possessed columns similar to the true crinoids, and were 

 attached to the ocean-bed as the crinoids were. I had long con- 

 sidered this as probable : and, on carefully re-examining my speci- 

 mens, I found one in which the indications of the fact are so apparent 

 that they almost force conviction that my first surmises were correct. 

 In the specimen alluded to the ambulacra are seen terminating at, 

 and against, a circular plate with radiating striae on its surface, and 

 close along side is a short portion of a column, each of the radii on 

 which is a fac simile of those on the body-plate, from which the 

 column has apparently been separated, and but slightly displaced by 

 the pressure that broke assunder the columnar support, and left it in 

 close proximity to its original place of attachment 



I was first led to entertain a doubt about Paleechinus being a free 

 echinoderm from finding portions of columns lying close to specimens 

 of that genus, and which I could not refer to any known crinoid. 

 The striae on the articulating surfaces of the circular columnar joints, 

 which probably belong to Paleechinus, are more deeply grooved near 

 their margin than in Actinocrinus, or other allied forms. 



Another circumstance that rather favours the supposition that 

 Palaechinus possessed a column is the fact that it is occasionally found 

 lying on its side, a position the true crinoids are mostly seen in ; and 

 as the lower or under side has a larger and more depressed surface 

 than the rotund, or highly convex, lateral ones, it is a natural in- 

 ference that some restraining influence produced this almost uni- 

 versal identity of position, and what more probable than that a 

 column was the cause of this uniformity ? Of course the presence of 

 a column would prevent the Palaechinus, after death, falling in any 

 other way than on its side. Among the numerous specimens which 

 I have examined, I have never met more than two that differed in 



