136 CRINOIDS EROM THE UPPER CHALK OF SOUTHERN SWEDEN. 



from its interradiai sides there proceed five linear oblong basals, 

 which do not quite reach the circumference. The outer end of each 

 is marked by an oval oblong impression. 



Diameter, larger specimen 8 millim., smaller 5 mm. 



Height, larger specimen, 2 millim., smaller 1*5 mm. 



Remarks. I do not know of any Comatula, either recent or fossil, 

 with a centrodorsal at all like that of this species, except Antedon 

 Tourtice. Schliiter * figures five slight grooves radiating outwards 

 from the radial pits of this last species ; but he makes no mention of 

 them in the text. The ventral surface of its centrodorsal is slightly 

 concave, with the angles raised ; but this is far less distinctly the 

 case than in A. impressa ; and the centrodorsal is half as high as it 

 is wide, and bears four vertical rows of cirrhus-soekets, characters 

 which distinguish it sharply from A. impressa. 



The persistence of the basals in connexion with the centrodorsal 

 rather than with the radials is also interesting. They are probably 

 the original embryonic basals (or orthobasals), as in A. Lundgreni 

 and a few other species f . If they were merely basal rays connected 

 with a rosette, some trace would have remained of such a connexion ; 

 but I can find none. 



EXPLANATION OF PLATE VI. 



Fig. 1. Mesocrinus Fischeri, G-eiuitz, sp., natural size. Copied from an 

 amended drawing of the original, kindly lent by Prof. Geinitz. 

 2. Calyx of Mesocrinus Fischeri, enlarged : a, side view ; b, dorsal 

 surface. 



3-6. Stem-joints from Kopinge, S. Sweden, probably belonging to 

 Mesocrinus suedicus, all X 2 : a, face views ; b, side views. 



7. Calyx of Mesocrinus suedicus, nov. gen. et sp., X 6 : a, ventral 

 surface ; b, dorsal surface ; c, from the side. 



8 & 9. Centrodorsals of Antedon impressa, n. sp. : fig. 8. Dorsal sur- 

 face of the larger specimen, X 4 ; fig. 9. Smaller specimen, x 6 : 

 a, dorsal surface ; b, from the side ; c, ventral surface. 



Discussion. 



The President expressed his sense of the value of the author's 

 communication, and hoped he would continue his work. 

 Prof. Duncan expressed the same view. 



Prof. Seeley said the variations of Boiirgueticriniis were very 

 remarkable, both in form and in structure of the calyx. He had 

 never seen one with the structure of that described, but had seen 

 some approaching it. He eulogized the description given by the 

 author, and expected from him important contributions to the 

 knowledge of the Cretaceous Crinoids. 



* " Uebsr einige astylide Crinoiden," Zeitschr. d. deutsch. geol. Gesellsch. 

 1878, p. 41, Taf. i. figs. 4-6. 



t Quart. Journ. Geol. Soc. 1880, vol. xxxvi. p. 550; Journ. Linn. Soc, Zool. 

 vol. xv. p. 213. 



