CALAMOCRINUS DIOMED.E. 41 



pinnule, the seconrl fork on the same side to the third pinnule, the third 

 fork on the left to the second pinnule. In the right anterior food groove, 

 the first fork leads to the fourth pinnule ; the second branch, the poste- 

 rior interradiuni, leads to the first pinnule, the third to the second, and 

 the fourth to the third pinnule. In the right posterior, the first fork leads 

 to the first pinnule, the second fork on tlie same side to tlie third pin- 

 nule, the third fork on the opposite side to the second pinnule, and the 

 fourth fork to tlie fourth pinnule. In the left anterior groove, the first 

 fork to the left leads to the second pinnule, the second fork on the oppo- 

 site side to the first pinnule; the third fork on the same side as the first 

 fork leads to the fourth pinnule. In the left posterior groove, the first 

 fork leads to the first pinnule, the second fork to the third pinnule, the 

 third fork to the second pinnule, the fourth fork to the fourth pinnule.* 

 The first and second forks encroach upon the left posteuior interradium, 

 the third on the anal. The joints of these lower first pinnules form a 

 solid arch over the food groove, bending as they do closelv upon the 

 surface of the ventral disk, and are in marked contrast to tlie other 

 pinnules along the arms and its forks, in wliich only one or two joints 

 cover the continuation of the perisomatic plating along the sides of the 

 arms. Compare Plate IV. Fig. 1, and Plate V. Figs. 1, 2, 4, with Plate V. 

 Figs. 5, 6, 7. 



De Loriol f says, " Nous ignorons encore comment s'operait I'occlasion de 

 la cavite qui renfermait les parties molles de I'aninuil. II parait fort proba- 

 ble que cette cavite etait recouverte non d'une voiite solide, comme dans 

 la plupart des Crinoids paleozoiques, mais d'une membrane fortifiee par de 

 nombreuses petites pieces calcaires qui leur donnait de la fermete." 



A few years later, de Loriol confirms this.+ for in 1887 he figures (Plate 

 III. Figs. 1, !"-«) the ventral disk of A. Roissyanus, so that we have for 

 the first time an accurate idea of its structure. The conical sac fio-ured 

 by de Loriol is covered with plates irregular in outline, thin, contiguous, 



* Carpenter in a letter calls attention to a curious point of resemblance between Metacrinus and 

 Calamocrinus in the characters of the disk. In both cases the ambulacra of the lower pinnules start 

 directly from the primary trunk, and not from its two forks, as in most Crinoids. See Plates 39 and 

 43 of the Challenger Report. 



t Note sur le Genre Apiocrinus. Association francaise pour I'Avancement des Sciences, Comptes 

 Rendus de la lime Ses.sion, p. 33-5 (p. 331). La Rochelle, 1882 (Paris, 1883). 



t Note sur quelques fichinodermes fossiles des Environs de la Rochelle, par P. de Loriol. p. 313. 

 Academie de la Rochelle, Societe des Sciences Xatuielles de la Charente Inferienre, Aunales de 1886, 

 Tom. XXIIT.. 1887. 



U 



