234 DEVONIAN FAUNA. 



of the greatly elongated ventral sac, which in its higher parts is covered by 

 slightly transverse quadrate plates, and swells out into a slightly clavate 

 form. 



Size. A calix is 3 mm. high ; another 6 mm. high. The arm of a similarly 

 sized specimen appears to be more than 50 mm. long. 



Localities. In the Barnstaple AthenaBum are one specimen from Braunton 

 and two from Roborough ; in the Woodwardian Museum are five (on four slabs) 

 from Barnstaple; and in the Porter Collection two from Pilton. 



Remarks. The great slightness and elongation of its arm-plates and the 

 length and mode of branching of the arms easily distinguish this form from the 

 accompanying Crinoids. The arms do not appear to exceed ten, and are com- 

 posed of alternately long and shorter quadrate plates, only the longer of which 

 appear to bear long and relatively strong pinnules, which, therefore, do not pro- 

 duce the usual plumose aspect. The arms do not seem straight, but slightly 

 waved or zigzagged, the pinnules starting from the outer angles thus formed. 

 Possibly the pinnules themselves sometimes have a slightly waving shape, and 

 hence they may be of rather doubtful nature, and possibly have to be reckoned as 

 armlets, but I have not been able to recognise any branching in them. 



The anal side of the cup is seen in a small specimen (PI. XXXVI, figs. 2, 2 a, 

 which I should regard as the type) which retains the arms ; but there it is rather 

 distorted by accident. This specimen also shows the ventral sac, which is seen to 

 rise from the anal plates of the cup for some distance as a narrow tube covered 

 with elongate hexagonal plates, and then to swell out into an elongate inflated 

 shape, when it is covered by short quadrate pieces in probably ten or twelve rows. 

 How high it extends cannot be seen. The height of the cup being about 4 mm., 

 the neck of the sac is 10 mm. long, and the inflated part more than 10 mm. ; while 

 the width of the neck is 1 mm., and of the inflated part 3 mm. 



The arm-plates are sometimes three times as long as their width. 



Two specimens (PL XXXVI, figs. 6, 8) were regarded by me in 1896 as a dis- 

 tinct species, which I named Poteriocrinus Batheri. They seemed to differ from 

 the type by the greater size and length of their basals, shorter colurnnars, and 

 some other points. Further examination makes me very doubtful whether any of 

 the supposed distinctions hold good, or may not have been really caused by the 

 imperfect preservation of our specimens the appearance of the column especially 

 being due to decay, and the portion of an arm (fig. 7) on the same slab as fig. 6 

 evidently belonging to another animal of a different species. They must therefore, 

 I think, be united with the present species. 



Affinities. Sc. loreus, Sladen, sp. 1 ( Poteriocrinus tenuis, Austin), is very 

 similar, and seems evidently congeneric, but its dorsal cup is more elongate and 



1 1877, Sladen, ' Proc. W. Kid. Yorks. Geol. and Potyt. Soc.,' n. s., vol. i, p. (5), pi. x, fig. 2. 



