THE TTPPEK CHALK OF S0UTHEEN SWEDEN. 



329 



than is the case in Bourgueticrinus. Both it and the joints imme- 

 diately below it are decidedly smaller than those forming the lower 

 part of the stem, which is just the reverse of what we find in Bour- 

 gueticrinus. 



Prof. Geinitz was unable therefore to refer this specimen to 

 Bourgueticrinus, despite the resemblance of its stem-joints to those 

 of that type ; but he supposed it to belong to the genus Antedon on 

 account of the resemblance of its calyx to that of Ant. Sarsii, as 

 represented by M. Sars in his well-known ' Memoires pour servir a 

 la connaissance des Crinoi'des vivants.' In the specimens figured 

 by Sars*, "the upper end of the stem is not thickened, and the 

 calyx widens from its base to the upper end of the first radial," just 

 as in the fossil from Strehlen (Geinitz f ). This resemblance is but 

 an imperfect one, however ; for Sars's specimens were merely the 

 stalked larvae of Ant. Sarsii, not more than an inch long. In the 

 later stages of these larvaaj the uppermost stem-joint or future 

 centro-dorsal piece of the mature and free Antedon not only becomes 

 considerably enlarged, so as entirely to conceal the basals, but it 

 also bears cirrhi. This, however, is not the case with the corre- 

 sponding joint of the Strehlen fossil. 



Prof. Lundgren § has already pointed out that this specimen is 

 too completely developed to be a larval Antedon like those figured 

 by Sars ; but neither he nor any other paleontologist has referred 

 it to any definite position among the Crinoids. 



The " Mucronatenkreide 99 (= Upper Chalk) of Kopinge, near 

 Ystad, in Southern Sweden, contains a quantity of stem -joints 

 (PI. YI. figs. 3-6) which have been considered as belonging to 

 Bourgueticrinus ellipticus, though no calyx of this species has yet 

 been found associated with them. Some years ago, however, a 

 singular calyx was met with (PI. YI. fig. 7), which was presented 

 to the Geological Museum of the University of Lund by Herr Rector 

 Bruzelius, of Ystad, into whose hands it had come. Its discovery 

 was announced in the ' Neues Jahrbuch fur Mineralogie ' by Prof. 

 Lundgren, who at once recognized its resemblance to the so-called 

 Antedon Fisclieri of Geinitz (PI. YI. fig. 2). It is, however, con- 

 siderably larger and much less conical ; but it has even less resem- 

 blance than the Strehlen fossil has to the cylindrical Bourgueticrinus 

 cequalis. During my recent visit to Lund for the purpose of 

 examining the Comatulce of the Hetzian collection, Prof. Lundgren 

 showed me this fossil, and was kind enough to intrust it to me for 

 description. Por this and for many other acts of kindness I offer 

 him my heartiest thanks. 



Por these two fossils, so similar in their general characters though 

 differing in points of detail, I believe that not only a new genus, 

 but also a new family must be established. I propose to call the 

 genus Mesocrinus ; for while allied to Bourgueticrinus in the cha-- 

 racters of its stem-joints, it is quite as closely allied to the Penta- 

 crinidse in the characters of its calyx. The only real resemblance 



* Op. cit. pis. v., vi. f Op. cit. p. 18. \ Op. cit. pi. vi. fig. 24. 



§ Neues Jahrbuch fur Mineralogie, 1876, pp. 180-182. 



