HISTORY OF THE CRINOIDE^. 9 



accordance with the ideas of Rosinus. From the date of this 

 discovery it may be said that the animal origin of the fossil Crinoids 

 was perfectly well established ; but no advance was made towards 

 their classification, upon principles deduced from the relations of the 

 different parts of the skeleton, until 1821, when Miller published 

 his work, "The Natural History of the Crinoideas."* 



In this work Miller shews that the calcareous plates which 

 constitute the frame of an encrinite have a quinquepartite arrange- 

 ment, or consist of five similar sets of plates, which, when spread 

 out in a plane with the base of the cup for a centre, assume the form 

 of a star with five rays. He also pointed out how the genera could 

 be founded upon the various modifications of these rays and upon 

 the number and position of the other plates, such as the sub-radials 

 and inter-radials. Up to the present time scarcely any improvement 

 has been made upon the generic system of Miller. The nomencla- 

 ture devised by him however for the different plates has been found 

 inconvenient, and others much more useful in application have been 

 substituted. The rules for the construction and determination of 

 genera used by all subsequent authors are essentially those of Miller, 

 and to him, therefore, belongs the credit of having first correctly 

 analyzed the skeleton of the Crinoideae. 



In June, 1835, the famous discovery of Thompson, that, in the 

 young state, the Comatulce so abundant in some of the existing seas 

 are true Crinoids, was communicated to the Royal Society.t In that 

 paper it was shewn that, at certain seasons of the year, the grooves 

 in the pinnulee of the rays of Comatula Europcea are filled with eggs 

 to such an extent that the soft skin which covers the furrow becomes 

 greatly distended, and that shortly afterwards the eggs are discharged 

 and myriads of them distributed about upon sea-weeds, shells, and 

 other marine objects. At first a short, thick stalk, supporting a 

 small, club-shaped head, which exhibits only obscure indications of 

 arms, springs from the deposited egg ; but soon the stalk increases 

 in length, the arms are unfolded, and a perfect Crinoid is thus 

 produced from the egg of a Comatula. The form and structure so 



* A Natural History of the Crinoidea or Lily-shaped. Animals, with observations on 

 the genera Asteria, Euryale, Comatula and Marsupites. 4to. 50 colored plates. By 

 J. S. Miller, A.L.S. Bristol, 1821. 



t Memoir on the Star-fish of the genus Comatula, demonstrative of the Pentacrimis 

 Europceus, being the young of our Indigenous Species. By John V. Thompson, F.L.S., 

 Deputy Inspector-General of Hospitals. Communicated by Sir James McGrigor, F.R.S. 

 Edinburgh New Philosophical Journal, volume xx., page 295. 



