222 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 88 



Post m. No anal plates in cup. The entire area of the post IR up 

 to the level of the arm bases is occupied by the hypertrophied 

 post B. Resting on the distal faces of this B are two large 

 plates which can be considered only as tube plates. 



Ventral sac. Judged from the proximal portion of the ventral sac 

 as preserved, the tube was relatively slender, subcylindrical in 

 shape, and composed of fairly large plates. 



Column. Stout, circular in section, composed of alternate nodals 

 and internodals. Lmnen large, outline indistinct in polished 

 section but apparently pentagonal. 



Species. The only known species referable to C estocrinus is the 

 new species G. striatus, here described. 



Geologic and geographic distribution. — The type species was found 

 in the upper Borden (Mississippian, lower Carboniferous) of Indian 

 Creek, Montgomery County, Ind. 



Relationships. — The peculiar structure of the posterior mterradius. 

 together with similarities of arm structure and general resemblance, 

 seems clearly to ally G estocrinus with Lecythocriniis jVIiiller and 

 Gorynecrimis Kirk. Of the two formerly described genera, Gesto- 

 crinus more nearly resembles Gorynecrimfs. The two genera differ 

 in well-marked structural characters. In Gorynecrinus the post B 

 is but slightly larger than the other BB. In Gestocrinus the post B 

 is very large, reaching to the level of the arm bases. In Goryne- 

 crinus the IBB are very small and scarcely visible in lateral view. 

 In G estocrinus the IBB are large, approximately one-third the height 

 of the cup. The arm-bases in Gestocrinus are sharply elevated above 

 the level of the RR and are relatively narrower than in Gorynecrinus. 

 As seen, there are many more IBr in Gorynecrinus than in Gesto- 

 crinus. In Gorynecrinus the two proximal tube plates lie well down 

 in the cup, and the tube plates of the second range rest on the upper 

 sloping shoulders of the r and 1 post RR. In Gestocrinus the pair 

 of proximal tube plates have been raised above the level of the cup 

 and rest on the upper sloping shoulders of the r and 1 post RR. 



The persistence of this tenuous genetic crinoid line from the 

 Middle Devonian well up into the lower Mississippian is very inter- 

 esting. Gestocrinus shows no resemblance to any known Carbonif- 

 erous inadunate genus, and one must cast back into the Middle 

 Devonian to find like structural forms. At all times members of 

 the family seem to have been exceedingly few in number. Lecytho- 

 crinus is represented by a few specimens. Goryneci^inus is known 

 from but a single specimen. Gestocrinus, also, is based on a unique 

 specimen. Since many thousands of crinoids have been collected at 

 Crawfordsville and Indian Creek, Ind.. as well as from approxi- 



