IS C. D. Walcott — Paleozoic Pterapods. 



vol. xxi, No. 11, p. 42, figs. 3-8, 1874), which Lindstrom sug- 

 gests is, by the thick-shelled Conularia fecunda Barrande, linked 

 to Conularia? and made to stand in affinity to them. (Sil. Gas- 

 teropoda and Pteropoda of Gotland, p. 41, 1884.) From our 

 comparisons Matthevia appears still more to serve as a connect- 

 ing link between Paltenigma and the genera Conularia and 

 Hyolithes. If P. Wrangeli had chambers running up into the 

 shell, as is suggested by the cross-sections, and a septum that 

 caused the upper portion of the shell to be decollated, as we 

 are led to believe by the natural section, and the fact that each 

 specimen figured has lost its apex, the relations between Palas- 

 nigma and Matthevia are quite close and Palasnigma may be 

 provisionally grouped with the genera Matthevia and Conularia. 



Matthevia variabilis, n. sp. 



On a side view, the outline of the shell varies from broad to 

 narrow conical, and the end view shows an elongate conical to 

 a broad conical outline ; the cross-section varies from elliptical 

 to oval or rounded quadrangular ; aperture varies in outline 

 with the proportions of the shell ; a sinus, varying in depth 

 and curvature, extends across the ends of the shell; in the 

 more elliptical apertures the sides are nearly straight and par- 

 allel, while, in those with a subquadrangular outline, they are' 

 strongly curved, and the sinus at the ends is very profound. 

 The shell thins out at the edges and is not thick over the exte- 

 rior of the interior chambers, but between them a connecting 

 mass of shell unites the sides and gives strength and solidity ; 

 a section, crossing the center of the shell at right angles to the 

 preceding, shows a solid shell to the outer chamber where it 

 gradually thins out to the margin. The position of the two 

 inner chambers vary in relation to each other, from subparallel 

 to widely divergent; the chamber that is more at right angles 

 to the aperture than the other, is usually larger, and is always 

 prominent, while the oblique chamber is sometimes filled up 

 by shelly matter and only the outer portion remains ; both 

 chambers are usually flattened on the inner side, and more 

 or less expanded where they enter the large outer chamber. 

 The septum crossing the inner chamber is thin, and varies in 

 shape with the form of the chambers ; it is usually slightly 

 concavo-convex, concave towards the outer chamber, and 

 marked, usually, by a raised scar of varying character; the 

 septum is usually a short distance from the outer chamber — 



I mm 4-,-s Mm 



. The substance of the shell is calcareous. 



• Surface marked by undulating lines of growth parallel to the 

 margin of the aperture, a few radiating lines usually on the 



