50 FOSSIL MEDUSA. 



preserved, and the casts do not even show any trace of its sculpture. We are also left 

 in the dark in regard to the position and nature of the organs most important for classi- 

 fication, such as the mouth, the anus, etc. Such being the case, it is impossible to 

 determine with certainty their place in the system, and their relation to each other, 

 all the more because in many cases it can not be decided to what extent the differ- 

 ences are to be attributed to the changes to which the casts were subjected after their 

 first formation. Such changes readily occurred before the mass hardened by reason 

 of pressure or other external agencies, which is rendered evident by the fact that 

 most of the specimens are more or less oblique. Nevertheless, these fossils are of 

 great interest as the oldest representatives thus far known of their class, and for that 

 reason I deemed it incumbent on me to give a description of them, however unsatis- 

 factory it necessarily must be. For the reasons given above, their affinities can not 

 be made out with any degree of accuracy. Professor Loven is inclined to regard 

 them as Cystidese, perhaps related to Agelacrinus, and accordingly I have provision- 

 ally given the above name to the form which seems most constant. Its outline is 

 either circular or more or less distinctly five- or four-sided, with the corners rounded 

 off. One side is of low conical form, sometimes nearly hemispherical. It bears four or 

 five radiating ribs, which proceed from the point and extend to near the edge. There 

 they are nearly always broken; it is found, however, that they had prolongations 

 which extended beyond the edge and formed free arms. A few specimens, which are 

 attached to sandstone plates, and one of which is represented in fig. 10, show long, 

 narrow arms; still, the specimens are so indistinct that it can not be made out with 

 certainty whether they belong to this species. The opposite side for the most part 

 appears nearly even, with a slight circular depression in the middle. In one speci- 

 men (figs. 8, 9) it iias an altogether peculiar structure, bearing on the periphery five 

 oval, strongly marked elevations, each of which corresponds to one of the radiating 

 ribs on the other side. If these are imagined absent, the form will be the usual one. 

 Agelacrinus ( ?) lindstromi was found by me at Lugnas only, and even there not in 

 special abundance. Usually, however, several specimens are found together. They 

 are often embedded in clay slate, so that they can be detached. To be able to explain 

 this fact, taken together with their nature as casts, it must be assumed that they are 

 not altogether complete. Some part of the animal must have risen above the clay 

 mud, so that after its dissolution an opening was left through which sand, when it 

 began to be deposited, might enter, and one is led to think that the sandstone tube, 

 which gradually filled up this opening and connected the casts with the sandstone 

 stratum formed above the clay bed containing the casts, was broken oft'. On the 

 specimen collected, however, no trace of such a break can be discovered. Even when 

 I found them still embedded in the clay slate nothing touching this subject could ever 

 be made out, for the clay slate was always in such condition that when the casts were 

 loosened from it it crumbled to pieces, together with the small cavities filled with 

 sandstone, in form of arms and the like, connected with the casts. A more accurate 

 investigation of the structure of the animal must, therefore, be left to the future, 

 together with the explanation of the remarkable difference in the structure of one 



