154 PROCEEDINGS OP THE ACADEMY OP 



as well as in the plates of the lower part of its body being much more dis- 

 tinctly tubercular, and in the greater number and more crowded arrangement 

 of its arms, which were evidently, at their bases, directed outwards, instead 

 of being, from their origin, directed obliquely upwards. 



From our A. pistilliformis, with which it agrees more nearly in some re- 

 spects, it differs, not only in having three more arms, but in the less abruptly 

 contracted form of its body immediately below the arms, as well as in having 

 from four to six interradial pieces to each space, instead of only two or three. 

 There were doubtless other more important differences that would be apparent 

 on comparing perfect specimens of each, judging from the different geological 

 positions of these two forms. 



Locality and position. Burlington limestone, of subcarboniferous series, 

 Burlington, Iowa. 



Subgenus SPHiEROCRINUS, M. & W. 



Actinocrinus (Sph^erocrinus) concavus, M. & W. 



Actinocrinus {Amphoracrinus) concavus, M. & W. Proceed. Acad. Nat- Sci., 

 Phila., June, 1861, p. 132. 



This curious little species may be regarded as the type of a section of the 

 group Actinocrinus, as usually understood, for which we would propose the 

 name Sphcerocrinus. Its peculiarities consist in the deep convexity of the 

 base, and the tumid and curved character of its first radial and first anal pie- 

 ces. These characters are so marked, that when placed with the under side 

 down, it rests directly upon a broad base formed of the first radial and first 

 anal pieces, which curve under to connect with the sunken basal pieces, and 

 upwards to form a part of the vertical walls of the cup. In the lateral position 

 of its anal and oral opening, it agrees with Agarricocrinus and Amphoracrinus ; 

 but it differs from the first, with which it also agrees in being concave below, 

 in the tumid and curved character of its first radial and anal pieces, as well as 

 in having the succeeding radials, anals, and interradials forming a vertical 

 wall, instead of extending out on a horizontal plane, while its arms are very 

 much weaker, and rise from around the summit, instead of from the horizon 

 of the lower part of the body. Its interradial and second range of anal pieces 

 are also much shorter. 



From Amphoracrinus, it not only differs in tbe concavity of its base and the 

 curved character of its first radial and first anal pieces, but in all the other 

 peculiarities of form, and the weakness and position of its arms. 



From Dolatocrinus, Lyon, (Cacabocrinus, Troost ?) with which it agrees in 

 form, the number of basal pieces, and the sunken condition of its base, as well 

 as in the incurved character of its first radials, it differs in having its first 

 anal piece down on the same range with the first radials, and connecting with 

 the base as in the typical forms of Actinocrinus, instead of being up on a range 

 with the first interradials. It also differs in its lateral anal and oral opening, 

 as well as in not having protuberant arm bases. 



MOLLUSC A. 

 CEPHALOPODA. 



GoNIATITES COMPACTUS. 



Shell subdiscoid ; umbilicus wide, or about twice the dorso-ventral diame- 

 ter of the last turn near the aperture, moderately deep, and showing about 

 half of each inner turn. Volutions four, near twice as wide as their diameter 

 in the direction of the plane of the shell, broadly rounded externally, and 

 each provided with a broad moderately deep concavity on the inner side, for 

 the reception of the next whorl within ; sides rather narrowly rounded near 

 the umbilicus, and rounding off more gradually to the periphery, the most 



[Aug. 



