16 Liitken — On Pentacrinites and Sea-Lilies. 



3, The tail-ribs are duplicate. This is an essential difference. 



4. The axis is, generally speaking, narrower, and its width is nearly 



the same throughout : in Asaphus, the axis of the thorax 

 always greatly exceeds in width that of the tail. 

 These distinctions will draw a broad line between the two genera, 

 and will separate the British species belonging to them as in the list 

 that follows. There will be no intermediate or doubtful forms, with 

 the exception of Ogygia f hybrida, — of which the tail only has been 

 hitherto discovered. 



Asaphus — {Basilicus) tyrannus, Murch. Llandeilo Flags, Llandeilo. 



peltastes, Salter. Llandeilo Flags, Llandeilo. 



Fowisii, Murch. Llandeilo Flags, Anglesea. 



Marstoni, Salter. Caradoc Shale, Horderley, Shropsliii'e. 



latieosiatus, McCoy. Llandeilo Flags, Builth. 



(?) radiatus, Salter Caradoc, Rhiwlas, near Bala. 



{Ftychopyge) Corndensis, Murch. Llandeilo Flags, Builth. 



{Isotelus) ffiffas, Dekay. Caradoc Rocks, Tyrone. 



ajinis, McCoy. Up. Tremadoc Slate, S. of Portmadac. 



Homfrayi, Salter. Up. Tremadoc Slate, near Tremadoc. 



{Brachyaspis) rectifrons, Portl. Lower Silurian, Tyrone. 



{Cryptonymus) scutalis, Salter. Caradoc, Tyrone. 



Ogygia — Buchii, Brongn. Llandeilo J^'lags, Builth. 



„ var. convexa Llandeilo Flags, Builth. 



„ var. angustissima. Llandeilo Flags, Builth. 



iLr. and Up. Tremadoc and Arenig 

 Tremadoc, Tortmadoc, and St. 

 David's. 



peltata, Salter. Arenig Group, St. David's. 



Selwynii, Salter. Arenig Group, Dolgelly. 



(?) hybrida, Salter. Llandeilo Flags? — Carmarthenshire. 



IDTOTICIES OIF nVCEIMIOIE-S 



I. — On the Pentackinites of the West Indies ; with some remarks 

 ON Pentacrinites and Sea-lilies in general.^ 



By Dr. Chkistian LiItken, Assistant Zoologist in the Museum of Copenhagen. 



Translated from the original Danish, hy Dr. Gustap Lindstrom, of Wishy, Island 

 of Gotland, Sweden. 



IN this very elaborate memoir, the author first describes a new 

 species, Pentacrinus Mulleri, and gives an excellent plate of the 

 animal, natural size. He then gives an account of the other 

 Crinoidea (Pentacrini, Holopus, etc.,) which have been found, or pre- 

 tended to have been found living, but the knowledge of them seems 

 to be very scanty and unsatisfactory. Next, Dr. Liitken compares 

 the Pentacrini with the genus Alecto, and states, that these genera 

 belong to the same natural family. The nearest allies of the Pentacrini 

 are, nevertheless, the extinct tertiary forms, (the true Pentacrini 

 from the London Clay, and the genera Isocrinus, H. v. Meyer, and 

 Gcenocrinus, E. Porbes). Of these Dr. Liitken considers the last as 



1 Om Vestindiens Pentacriner med nogle Bemarkninger om Pentacriner og Solilier 

 i Almindelighed of Dr. Phil. Chr. Liitken. Af Naturhist. Foren. Yidensk. Med- 

 deleser 1864. 



