INVERTEBRATES. 



191 



latter character may seem to be one of little importance, but when we remem- 

 ber that it is coexistent with the other distinctions, it becomes of more signifi- 

 cance than it would otherwise be. Where the specimens of Strotocrinus have 

 the margins of the expanded summit entire, they will be at once distinguished 

 from any known examples of Batocrinus, or the other type of the Actinocrinidae. 

 Eig- G - a As is known to be the case in several species of 



Actinocrinus, Agaricocrinus, etc., some species at 

 least, of Strotocrinus, were provided with a pecu- 

 liar, convoluted internal plate, resembling the 

 shell of a Bulla, or Scaphander, placed with its 

 longer axis so as to coincide with that of the body 

 of the crinoid. The annexed cut represents this 

 organ as it occurs in its natural position, in a bro- 

 ken specimen apparently of S. regalis, = ( Actino- 

 crinus regalis, Hall). As seen in the specimen, 

 however, it is thickly coated with small crystals of 

 carbonate of lime, not represented in the cut. 

 strotocrinus regalis. p ro f H a u mentions seeing a similar plate in S. 



th! h eTp£r?ded P su^ as well as in 



the side removed in order to exhibit . r> a • • /t\ n • • i 



the involuted internal organ con- species of Agaricocrinus (Deer, new sp. Crinoidea, 

 nected with the digestive apparatus. prelim _ NotioCj p> 12j 1861), but makes no sugges- 

 tions in regard to its nature or probable use in the internal economy of these 

 animals.* We have likewise seen this organ in Actinocrinus rotundatus, Yandall 

 and Shumard, and have little doubt but it existed in all the Actinocrinidae, and 

 possibly other families of palaeozoic crinoids. We regard it as corresponding to 

 the spongy axis and spiral plate around which the digestive canal in Gomatula 

 europsea passes, (see Muller's figures of this axis and plate in Abandl. Akad. 

 Wissinsch, Prelim., 1841, pi. 5). It differs, however, in being a simple plate 

 rolled up somewhat like a scroll of parchment, or the shell of a Scaphander, 

 instead of being wound around a spongy axis like the thread of a screw. The 

 discovery of such an organ in these older types of Crinoidea, is of much interest, 

 since it seems to settle the question in regard to their having been provided 

 with an internal digestive apparatus, as in the living types — a fact that has been 

 recently questioned by Dujardin and Hupe, who appear to think they were 

 nourished by absorption over the whole external surface. 



* Since the foregoing remarks were written, and the accompanying cut prepared, we 

 observe Prof. Hall has published in the March number of the Am. Jour. Sci., vol. xli, 

 p. 261, 1866, a note, in which he mentions seeing this plate in Actinocrinus longiroslris, 

 A. pentagonus, A. Verneuilii, and some of the forms we have included in Strotocrinus, 

 and states that on showing one of the specimens to Prof. Agassiz, he remarked that 

 he had seen a similar organ in Comatula. 



