.')() F. A. BATHER, CRINOIDEA OF GOTLAND. 



Herpetocrinus. 



(1'lates 1 and II, tigs. 24 — 78). 



(1852, Myelodactylus, Hall.) 



1865, Ophiocrinus, Ciiarlesworth non Salter 1856. 



1873, Herpetocrinus, Salter. 



1878, Myelodactylus, Angelin, pars. 



1879, Myelodactylus, Zittel. 



1879, »Myelodactylus?», Wachsmuth and Springer. 



1880, Myelodactylus, S. A. Miller. 



1880, Myelodactylus, Nicholson and Etheridge, 

 1889, Herpetocrinus, Bather. 



History of opinion. 



Not only the systematie position, but the structure and homologies of this genus 

 liavo long been obscure. 



In 1852 Prof. Jas. Hall proposed the name Myelodactylus 1 ) for certain stem- 

 ossicles, which he described as brachials. The only generic character pointed out by Hall 

 was the ' »foramen or medullary canal penetrating the column of joints». In no case, even had 

 the specimens been brachials, could this character have had a diagnostic value; for the pre- 

 sence of an axial canal is the rule in pinnulate arms. Prof. Hall, however, ga ve figures 

 and a clear, though erroneously worded, description of his type-species 2 ). From these 

 figures it shoukl have been clear that the specimens, whatever they were, were not the 

 brachials of a Crinoid; for the »tentacles» were represented as two to each ossicle. In no 

 Crinoid is tliere more than onc pinnule to a single brachial; such an occurrence is an 

 evolutionary impossibility. Prof. Hall also described M. brachiatus 3 ) and some uhnamed 

 fragments 4 ). His two species are distinct, as species go in this genus. 



In 1865 Mr. E. Charlesworth exhibited 6 specimens of this fossil a t a meeting of 

 the Birmingham Natural History Society on November 21st. His remarks were reported 

 in the Birmingham Gazette of November 23rd, and copied into The Reader a ). He proposed 

 the name Ophiacrinus for the genus, and regarded the remains as »detaehed fingers of 

 encrinites bearing encrinital-shaped tentacles». »The specimens exhibited were suftieiently 

 distinct inter se to indicate the existence of several species.» 



In 187.) J. W. Salter ( ') changed the name of this genus to Herpetocrinus (tpnhTOt', 

 a creeping thing), discarding Halls name »as based on false ideas». A t the same time 

 lic described the crown and the stem in correet terms. As type-species he took his new 

 species H. Fletcheri, which can be identitied from liis description and figure combined- 

 Unfortunately Salter was not content to draw what lie saw, but tried his hand at resto- 

 ration: the result was a monstrosity which made people doubt the accuracy of his dcscrip- 



') Nat. Hist. N. Y., Palaeontology, vol. II, p. 1!>1 — (tcelov, medulla and öaxTvÄog, digitus». 



2 ) Op. ett., p. 192, Pl. XLII, tigs. b a, b and 6 a—h. 



3 ) Op. rit., p. 232, Pl. XLV, tigs. 7 a—e. 



4 ) Op. eit., p. 232, Pl. XLV, figs. 8 a, i and a, b, c. 



5 ) The Reader, vol. VI, Part. XXXV, No. 152, p. 604; London, Saturday, Nov. 25th, 1865. 



6 ) Cat. Foss. (icol. Mus. Cambridge, p. 118. 



