THE UPPER CHALK OF SOUTHERN SWEDEN. 



135 



of P. asteria is not unlike that of M. suedicus (PL VI. fig. 7), which 

 has much more resemblance to it than to the calyx of any species 

 of Millericrinus. 



Despite the resemblance of their calicos to the Pentacrinus-type, 

 the so-called Antedon Fischeri and its Swedish ally obviously belong 

 to another genus than Pentaerinus. They lack the typical stem of 

 this genus, with its verticils of cirrhi from the top downwards and 

 the petaloid markings on the joint-faces. Neither does Mesocrinus 

 possess the typical stem of Apiocrinus or Millericrinus ; but while 

 chiefly resembling Bourgueticrinus in the character of its stem, it 

 differs from that genus and approaches RJiizocrinus in the compara- 

 tively small size of its upper stem-joints ; and it especially resembles 

 R. Rawsonii in the relatively slight increase in the diameter of its 

 calyx from below upwards. In neither case does the calyx pass 

 gradually downwards into the thickened upper end of the stem, as 

 it does in the typical Apiocrinidae and in Bourgueticrinus, to which, 

 in other respects, Mesocrinus has a considerable resemblance. 



The similarity of the articular faces of the stem-joints of the 

 young Antedon Sarsii to those of Rhizocrinus, and the imperfect 

 radicular processes that proceed from the lower part of its stem, are 

 characters which connect the Comatulidae with the Apiocrinidae. 

 The Pentacrinidse, however, are sharply marked off from the latter 

 family by the striking differences in the character of the stem. It 

 is therefore of no small morphological interest to find a type in 

 which the characters of a Pentacrinus-calyx. are combined with those 

 of a Bourguetic7*imis-stem. It is quite possible that some of the 

 stem-joints now referred to Bourgueticrinus may belong to other 

 intermediate forms, the calices of which are still unknown to us, as 

 that of Mesocrinus was but a few years ago. 



Prof. Lundgren has been kind enough also to intrust to me the 

 description of a new Antedon, two specimens of which were found 

 by himself and by Mr. J. Chr. Moberg in the Ignaberga Limestone 

 at Balsberg, in the province of Scania, S.W. Sweden. 



Antedon impressa, n. sp. (Plate VI. figs. 8, 9.) 



Centrodorsal a thin convex pentagonal disk with very indistinct 

 traces of a small five-rayed impression at the dorsal pole. In the 

 larger specimen the dorsal surface is somewhat flattened and tolerably 

 free from cirrhi (fig. 8), but in the smaller and younger specimen 

 there is but a very small cirrhus-free space (fig. 9, a). There are 

 about 40-50 sockets arranged in three rather indistinct rows, with 

 occasional traces of a fourth ; but they are too much worn to show 

 any structural details. 



The ventral surface is entirely obscured by matrix in the larger 

 specimen, and is only partly visible in the smaller one. It is 

 markedly concave ; and its angles are somewhat produced upwards 

 and outwards. In the middle line of each radial area is a median 

 groove, the central end of which is deepened and forms a radial pit. 

 The outline of the central opening was probably decagonal ; and 



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