250 PROFESSOR ALLMAN ON A PRE-BRACHIAL STAGE 



occupies a middle place between' Eugeniaa^inus and Haplocrinus, passing on the 

 one side, by the suppression of the inter-radial series, into Eugeniacrinus, and on 

 the other, by the suppression of the axillary series, into Hajylocrimis and the pre- 

 brachial fixed larva of Comatida. 



In the "Jahrbuch fiir Mineralogie" 1840, Hagenow describes, under the 

 name of Hertlia mystica, a small Crinoid from the White Chalk. The high 

 pyramidal roof of this little fossil, as figured by Hagenow, is one of its most 

 characteristic features, and presents so striking a similarity to the roof of our 

 young Comatnia, as to suggest the probability that its five triangular sides are 

 the horaologues of the parts which so closely resemble them in the latter animal 

 and in Hajjlocrinus. J. Muller, however, considers that the Hertha mystka is 

 only the centro-dorsal piece of a Comatida, with the first radialia still attached 

 and constituting the sides of its roof, a view which seems borne out by the 

 general structure of the fossil, though its remarkable form is certainly something 

 very different from anything presented by the same parts in the Comatuke of 

 the European seas. The discovery of additional specimens will probably clear 

 up some of the difficulties in the way of an entirely satisfactory solution of the 

 nature of this somewhat enigmatical little fossil. 



De Koninck and le Hon (Recherches sur les Crinoides du Terrain Carbonifere 

 de la Belgique) describe, under the name of Lageniocrinus seminulum de Kon., a 

 minute carboniferous fossil which they regard as a transitional form between the 

 Platycrinidw and the Blastoidea. The body of this little fossil is in the form of 

 a pentahedral cup, crowned by a high pyi'amidal five-sided lid, quite destitute of 

 arms, and even without trace of surfaces which could have served as points of 

 attachment for arms which might have at one time existed. 



If we adopt the interpretation of its composition as proposed by de Koninck, 

 we shall have a basis composed of three basalia (admitting, as in other similar 

 cases, of an easy analysis into the typical number five) ; while with these 

 there would alternate five radial series, each consisting of two radialia, all the 

 ultimate radialia converging towards the summit, in order to form the sides of 

 the roof If this be the true view, then, notwithstanding the striking resemblance 

 of Lageniocrinus to our larval Comatula, we must regard the roof of the latter as 

 formed upon an entirely different plan from that of Lageniocrinus. Adopting 

 DE Koninck's interpretation of the plates which enter into the formation of the 

 calyx, we may compare the five roof-plates to those which form the vertex in 

 Eugeniacrinus as described above, and therefore as properly axillary ; or the 

 flattened arms forming the roof of Cupressocrinus may also suggest themselves 

 as the true homologues of the roof-plates in Lageniocrinus. But it is also quite 

 open to us to regard the roof of Lageniocrinus as homologous with that of Haplo- 

 crinus or of our larva, only that in this case we must view the plates to which 

 DE Koninck assigns the place of first radialia as parahasalia, and we shall then 



