58 F. A. BATHER, CRINOIDEA OF GOTLAND. 



Calceocrinus, even if generically distinet from the forms now under consideration, would 

 at least belong to the same family, and if they are generically identical, Calceocrinus, 

 being the older name, would have to stånd for the typical genus». This argument no 

 longer holds good, for, as we have seen, the name Calceocrinus was not .justined till 1889. 

 Nevertheless it. would be a great pity to disturb the name Oalceocrinidse whieh has been used 

 by Dr Loriol, x ) Wachsmuth and Springer, Ringueberg, S. A. Miller, P. If. Carpextek 2 ) 

 and others. Palaeontologists therefore might well agree to retain Calceocrinus, Ring. as 

 the type-genus, especially as this genus ineludes not only the first known form of the 

 family, but also the majority of American, and, so far as known, all the European forms. 



Such are the conclusions to which we are led by a study of the literature; but 

 before we can absolutely accept all those conclusions we must consider the actual facts 

 presented by the fossils. To appreciate the Diagnostic characters of the genera, no 

 less than to frame a philosophical Terminology, it is necessary to investigate the Mor- 

 phology of the Family. 



No one has ever doubted but that the triangulär portion of the cup to which the 

 stem is attached, and from which the distal part of the cup is separated by a hinge, re- 

 presents a. number of basals more or less fused. Hall in his first specimens (1852) only 

 saw two plates in the base, but said: »It is probable that the plates are so closely anchy- 

 losed as to obscure or obliterate the lines of suture.» In describing Euchirocrinus cliry- 

 salis (1860), Hall recognised three plates in the base, of which one was triangulär with 

 sides paralie] to those of the whole base, while the other two lay along its sides and met 

 at the attachment of the stem. These three plates have now been seen in nearly all spe- 

 cies of the family: but it has further been noticed that in many forms, especially those 

 referred to the earlier genera Castocrinus and Euchirocrinus, the triangulär basal also 

 consists of two equal plates; thus the base would consist morphologically of four basals 

 more or less fused. In the låter species the articulation of the stem lies on the suture- 

 line between the two outer basals; but in earlier forms all four basals take part in the 

 articulation, so that the base approaches more nearly that of a normally symmetrical 

 crinoid. No one has hitherto pointed ont any relic of a fifth basal, but the above facts, 

 which are generally admitted, are enough to suggest that the earlier forms are, as one 

 would expect, the more ancestral. 



Castocrinus is the most primitive, not only in respect of its base, but also in the 

 structure and branching of the arms, which approach most nearly to the normal dicho- 

 tomous type. It may therefore be taken as proved that Castocrinus is the most ancestral 

 genus of the Calceocrinida?, and that its structure, in other points than those mentioned, 

 will be found to approximate to that of some more normal, but early Inadunate type. 



Let us then examine the scheme of the dissected cup of Castocrinus ( text-tig. 13 a). 

 Here are seen tive distinet radii. In these it is not very härd to decide which are the 

 radial elements in the strict sense, for the primibrachialia or costals rest in a slightly 



*) Paléont. Franpaise, vol. vi (Crinoides), p. 51, 1882. 



-) Nicholson and T,ydekkeh, Manual Pnla-ont., p. 440, 1890. 



