FOSSILS OF THE BUKLIXGTOX GKOUP. 357 



This species will be readily distinguished from all of the others pro- 

 vided with a ventral tube (so far as yet knowii) by the peculiar style of 

 the ornamentation of its body plates, its costae being more numerous, 

 and more distinct than in N. (egilops, S.glyptus and other similar forms. 

 Whether any of the other species were provided with so long a ventral 

 tube remains to be seen, as the specimens yet known all have this part 

 broken away. 



The specimen of the species under consideration, represented by 

 figure 2 fl, of plate 7, has the body crushed, and the ornamentation of 

 the body plates mainly obliterated by weathering. It also shows some 

 irregularity of the body plates, either due to accidental distortion, or to 

 abnormal development. The structure and ornamentation of the body 

 have, therefore, been described by us from the specimen represented by 

 figure 2 o, of the same plate. The other individual is figured to show the 

 greatly developed ventral tube. This tube doubtless possessed some 

 slight degree of flexibility during the life of the animal, but the bend 

 near its broken end seems not to have been due to flexibility, but rather 

 to abnormal development, by which the pieces on one side grew to larger 

 sizes than on the other, as may be seen by figure 2 b of the same plate, 

 which represents a side view of the curved point. How much longer 

 this tube may have originally been, it is not possible to determine from 

 the specimens, though it was probably not much longer than now seen, 

 though it is undoubtedly broken at the end. Immediately at the broken 

 end, a few little pieces are seen that look as if they might possibly 

 have, with others, partly closed the end. It is more probable, however, 

 that they belong to a part of the broken end, and have merely been 

 placed in the position they now occupy by accident. Unless the 

 tube tapered very rapidly, or was considerably produced beyond the 

 broken end, the opening would have apparently been rather large. 



Locality and position Upper part of the Burlington division of the 

 Lower Carboniferous series, Burlington, Iowa. No. 49 of Mr. WACHS- 

 MTTH'S collection. 



STROTOCRIXUS PERUMBROSUS, Hall (sp.) 



PI. 8. Fig. 4. 



Actinocrinu* perumbrotus, HALL. Supplement to Vol. L Part II. Iowa Report, p. 7. 

 Strotocrinu* perumbrosus, MKEK and WORTHBX. Illinois Geol. Report, Vol. U, p. 189; 1866. 



BODY presenting the usual urn-shape characteristic of the 

 typical species of the group, being more or less elongate- 

 obcouic below the spreading summit, and nearly flat on top. 

 Base more than twice as wide as high, and truncated below 



