264 PROCEEDINGS OE THE ACADEMY OF 



The typical specimen does not show the position of the siphon, hut a frag- 

 ment found near the same locality, and at the same horizon, apparently of 

 this species, though possibly belonging to another shell, lias the siphon placed 

 about its own breadth outside of the centre. It pierces the septa from with- 

 out inwards or backwards, as in Nautilus. 



At a first glance this shell would seem to resemble Cryptoceras (Lituite.s) 

 undatus, as represented by fig. 3, pi. 13, vol. i. Pah-eontology of New York, 

 but on a closer inspection, it will be at once seen to differ materially in the 

 more rapid increase in the breadth of its whorls, and in the proportionally 

 smaller size and greater depth of its umbilicus, as well as in being apparently 

 not coiled on a plane. 



The specific name is given in honor of Dr. 0. P. Baer, of Richmond, Indi- 

 ana, to whom we are indebted for the use of the typical specimen. 



Locality and position. Richmond, Indiana. From the Cincinnati Group of 

 the Lower Silurian Series. 



ARTICULATA. 



CRUSTACEA. 



TRILOBITA. 



Genus DALMANIA, Emmerich, 1845. 



Dalmania DanjE, M. & W. 



Attaining a large size, entire outline ovate, approaching subelliptic. Ce- 

 phalic shield rather compressed, nearly semicircular, about twice as wide as 

 long, rounded in front, and nearly straight or slightly concave in outline be- 

 hind, with posterior lateral angles produced into mucronate spines extend- 

 ing backwards to the fourth thoracic segment. Glabella composing rather 

 more than one-third the entire area of the shield, but slightly more convex 

 than the cheeks ; including the neck segment, as long as its greatest anterior 

 breadth, and about twice as wide in front as behind ; separated from the 

 cheeks on each side by a well defined furrow ; anterior lobe composing about 

 half its entire area., transversely elliptical, and a little less than twice as wide 

 as long ; lateral furrows well defined, anterior one oblique ; the other two 

 transverse, and not always strongly defined quite out to the lateral margins ; 

 anterior lateral lobe longer, more oblique, and at its outer end wider, than 

 either of the other two. Occipital segment widest and most prominent in the 

 middle, scarcely equalling the transverse diameter of the posterior extremity 

 of the glabella ; neck furrow well defined, but deepest on each side, and arch- 

 ing a little forward in the middle ; its continuations across the posterior sides 

 of the cheeks broad, deep, and straighter than the posterior margin, extending 

 nearly to the lateral margins of the cheeks, where they curve a little back- 

 wards. Cheeks sloping slightly around the outer side, to a broad, shallow, 

 undefined marginal depression, outside of which there is a moderately thick, 

 somewhat rfcunded border, which does not extend entirely around the front 

 of the glabella, but continues back into the posterior lateral spine. Eyes 

 reniform, not oblique, nearly half as long as the antero-posterior diameter of 

 the front lobe of the glabella, and situated slightly more than their own length 

 in advance of the posterior margin of the cheeks ; with (in casts) a moderately 

 distinct marginal furrow around their outer bases, (height and other details 

 unknown) ; palpebral lobes semicircular and depressed. Facial sutures cut- 

 ting the lateral margins of the cheeks nearly opposite the posterior extremities 

 of the eyes, and passiug around the antero-lateral and front margins of the 

 glabella, so near the anterior border as scarcely to leave any perceptible band 

 connecting the movable cheeks around the front. 



Hypostoma obscurely subtrigonal, about one-eighth wider posteriorly than 

 its length, moderately convex ; anterior margin forming a broad, regular con- 



[Dec. 



