46 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.54. 



acteristics). Except for the presence of a distinct clavicle, this 

 species might, on morphologic grounds, be classed with Paracyclas. 

 Another specimen (M 1799) represents the same form. 



Formation and locality. — Pembroke formation, gray, splintery 

 shales, Kelley Point, south shore of Pennamaquam River (loc. 5.3.2 A). 



Type-specimen.— Cat. No. 62890, U.S.N.M. 



REMARKS UPON THE SPECIES N. GALEUS, N. PELOPS, AND N. 



EURYLOOHUS. 



On plate 11a figure is given (fig. 19) of a slab of the splintery shale 

 from the Kelly Point locality (loc. No. 5.3.2 A) showing examples of 

 these three species as they, at present, lie upon the surface of the shale. 



At the top of the plate separate figures are given of each species 

 oriented as is customarily done in preparing plates to illustrate fossil 

 species. The straight lines drawn across the faces of the separate 

 figures represent the long axis of the splintery slab upon which they 

 lie, thus indicating roughly the direction in which the specimens 

 have been distorted. 



On the same plate, figure 7, is a more perfect specimen from the 

 same shales of the species N. pelops, and its orientation in relation to 

 the long axis of the splintery shales is the same as the specimen figured 

 above it (fig. 3) seen on this particular slab (fig. 19). 



This presentation of the facts will make it clearly evident that the 

 morphologic characters upon which the specific descriptions are (and 

 must be) based have been greatly affected by distortion incident to 

 movement of the containing rock after the shells were embedded. 



Paleontologists are familiar with this fact, but may not be aware 

 of the great difficulty there is in determining from the literature, or 

 from the actual specimens in museums, whether distortion has or has 

 not taken place. 



NUCUUTES LENTUS, new species. 



Plate 12, figs. 6 and 13. 



1860 cf. Clidophorus elongatus Hall, Canadian Nat. and E., vol. 5, p. 150. 

 Also Dawson, T. W., Acadian Geology, ed. 4, 1891, p. 601, fig. 206. 



This species agrees in so many particulars with the definition given 

 to OlidopTiorus elongatus Hall from the Silurian at Arisaig, Nova 

 Scotia, that the definition will be given entire and note made of points 

 of divergence from that definition. 



Hall's definition is as follows: Clidophorus elongatus, Hall, figure 

 206.^ Shell subelliptical, length about twice the height, beak much 

 nearer to the anterior end, which is narrowly rounded; umbones 

 rounded, promment ; a defined gradually widening depression extends 

 from the umbo to the posterior basal margin, causmg a straightenmg 

 or slight sinuosity in the edge of the shell; a defined ridge along the 



' The quotation is made from Dawson's Acadian Geology, 4th edition, p. 601. 



