CONTHIBUTIONS TO PAL.?EONTOLOGY. 169 



GENUS ARIONELLUS ( Barrande). 

 ARIONELLUS BIPUNCTxVTUS. 



PLATE VII. FIGS. 50 & 51. 

 Arionellus hipunctatus : SntrMARD, Trans. Acad. Sciences St. Louis, VoL ii, No. 1, p. 101* 

 The following is Dr. Siiumard's description of this species : 



** Small, moderately elevated. Glabella convex, conical, truncated 

 " or sometimes very gently arched at apex : length, excluding 

 " the neck-segment, equal to the width at the base ; sides gently 

 *' convex ; neck-furrow straight, moderately deep and well de- 

 " fined ; neck-segment short, semielliptical, with the sides gently 

 *' rounded. Dorsal furrows distinct all around, as deeply im- 

 " pressed as the neck-furrow, and marked opposite .each angle 

 " of the glabella in front with a minute circular depression. 

 *' No lateral furrows visible on any of the specimens under 

 " examination. Front margin rounded, and occupying about 

 *' one-fourth the total length of the head. 



** Movable cheeks regularly convex, margined with a narrow 

 " rounded raised border : genal angles prolonged into long 

 *' slender curved spines. 



" Length of head, 0*22 of an incli ; length of glabella, 0*16 ; 

 ** greatest width, O'll. The general contour of the head of this 

 *' species, when deprived of the movable cheeks, reminds one 

 *' of the head of Homolonotus delpkinocephalusJ' 



Through the kindness of Dr. Shumard, I have received specimens of 

 this pretty little species. In the form of the glabella, it resembles some of 

 the smaller species of Conocephalites ; hut the direction of the facial 

 suture, and the form of the palpebral lobe, are distinguishing features. 

 At the same time, the form of the associated movable cheeks is nyt unlike 

 many of those which occur with, and are referred to the smaller species of 

 Conocephalites, while the fragments of thoracic segments are likewise 

 of similar character. 



The minute depressions, or puncta, at the anterior angles of the glabella, 

 are well preserved in many specimens, while the occipital ring often bears 

 a small obtuse spur. The minute pits in front of the glabella are well 

 marked ; but these are not peculiar to this species. 



I follow Dr. Shumard in placing this species under Arionellus, though 

 it appears to me distinct from that genus, and not gencrically different from 

 some of the preceding species. 



From the associated fossils, I infer that this species occurs about the 

 middle of the sandstone, "near the mouth of Lawrence creek, a small 

 tributary of the St. Croix river, Minnesota ; " and from the mouth of Root 

 river in Minnesota, in the same horizon. 



[Senate, No. 115.] 22 



