508 HERRICK E. WILSON 



the type may have been derived by the simultaneous anchylosis 

 of the five primary plates, or from the closure of the remaining 

 sutures in any of the thirty possible combinations given above. 

 Dealing here with results alone, we see that thirty-one possible 

 modifications of the five primary basals are obtainable through 

 simple anchylosis. 



[To be continued] 



EXPLANATION OF PLATES 



PLATE I 



Teleiocrinus umbrostis Hall. Abnormal specimen cited by Wachsmuth and 

 Springer as confirmation of their theory 



No. i. — Oblique view of posterior interray, showing absence of anal plate 

 and one of the first interbrachials, and the reduction of the right-posterior basal. 

 Basal formula, ab — cd — e—; formula of posterior interray, o — 1—3—4 — 2 — . 



No. 2. — Mew of right-posterior interray, showing normal arrangement of 

 interbrachials 1 — 2 — 2 — 2 — , and reduction of right-posterior basal. 



No. 4. — Posterior view. 



No. 6. — Tegmen, showing position of anal tube. 



Teleiocrinus umbrosus Hall. Springer collection; normal specimens 



Fig. 3. — Posterior view, showing normal posterior interray and normal 

 base. Basal formula, ab — cd — ex— ; formula of posterior interray, A— 2 — 3— 

 4 — 1 — . To be compared with Nos. 1 and 4. 



No. 5. — Tegmen, showing position of anal tube in another specimen; to 

 be compared with No. 6. 



PLATE 11 



Glyptocrinus decadactylus Hall. Springer collection, specimens having a 



pentagonal base 

 No. 1. — Basal view, showing normal pentagonal base with five basals. 

 Basal formula, a — b — c — d — c — . 



Chicagocrinus inornatus Weller (type). University of Chicago Paleontoiogical 

 Collection, No. 10787 

 No. 2. — Basal view, showing anchylosis and reduction of antero-lateral 

 basals and compensating enlargement of postero-lateral basals. Basal formula, 



a — b — cd — c—. 



Melocrinus calvini Wachsmuth and Springer. Springer collection 



No. 3. — Posterior view. 



No. 4. — Basal view of same specimen, showing anchylosis and reduction 

 of sinstro-lateral basals and compensating enlargement of posterior and right- 

 anterior basals. Basal formula, a — bc—d — c—. 



