1 66 



THE CRINOIDEA 



to circular, but the columnals still alternate in size. From the imagined 

 intermediate form (not from Abacocrinus itself } Periechocrinus may have been 

 derived by fusion of 2 BB. FAMILY 3. CARPOCRINIDAE. Batocrinoidea 

 with 3 BB (? fused in Macarocrinus) ; RR rather large ; each half-ray 

 contains 1-3 IIBr usually passing into the free arms, which are usually 

 2, occasionally 3, to each ray ; iBr 2-5, in contact with iAmb ; illBr 

 may be present in limited and definite number ; tegmen of numerous 

 small plates, with a few larger ones ; in post. IR a vertical row of anals ; 

 stem large and round, usually with small pentagonal lumen. Genera 

 Acacocrinus, W. & Sp. (1897), Silurian, Indiana, has 2 arms to each 

 ray ; brachials wedge-shaped, each bearing one pinnule. Desmidocrinus, 

 Angelin (1878), Silurian, Europe ; in each ray one of the rami forks 

 again almost immediately. Macarocrimis, Jaekel (1895), Lower Devonian, 



Fio. LXXIX. 



Anns of Carpocrinidae. 1, 

 Macarocrinus Springeri (after 

 Jaekol). 2, Carpoci-imis sim- 

 pler- (based on Brit. Mus. 5536 

 & 57360). 



FIG. LXXX. 



Barrci ndcocr inns sccptrnm. 1, reconstruction 

 of the crown, with three of the rami removed 

 (after G. Liljevall in W. & Sp.). Nat. size. 2, 

 diagram of the calyx. Lettering as usual. 



Eifel, differs in greater length of Br, in fusion of BB, and presence 

 of one IIBr instead of two (Fig. LXXIX. 1). Carpocrinus, J. Miiller 

 (1841 ; synn. Phoenicocrinus, Austin ; Abracrinus, d'Orb. ; Hak'ocrinus, 

 Pionocriniu, and [?] Leptocrinus, Angelin, 1878. See W. & Sp., 1881), 

 Silurian, Europe ; derived from Desmidocrinus by fusion of free Br to 

 form uniserial ossicles each supporting 2 or more pinnules, and by atrophy 

 of the unpaired ramus, which resembles a large proximal pinnule (Fig. 

 LXXIX. 2). FAMILY 4. BARRANDEOCRINIDAE. Batocrinoidea with 

 3 BB ; RR irregularly shaped ; each half-ray containing 1 IIBr, which 

 supports a free arm, biserial, and recumbent over dorsal cup ; iBr, 3, in 

 contact with iAmb ; tegmen solid with large sub-spinous O, alternating 

 with 5 radial dome-plates ; stem large and round. . Genus Barrandeo- 

 crinus, Angelin (1878 ; syn. [?] Cylicocrinus, S. A. Miller non Miiller ; see 

 W. & Sp., 1897), Silurian, Gotland and (?) N. America (Fig. LXXX.). 



