TB rSNTON FA UNA OF BAFFIN LA ND-SCSUCSEBT. 171 



often three times the depth on the dorsal side. The siph uncle is very 

 small, almost in contact with the ventral wall, and swells but little 

 between the septa. 



Professor Whiteaves, who saw the type, states that among the frag- 

 ments of Cyrtoceras from Manitoba "are some apparently like C. cor- 

 7ii(lum in section, curvature, and much in the position of siphuncle." 



Collectors.— A. V. Shaw and A. H. White. Cat. No. 28121, U.S.N'.M. 



CYRTOCERAS BAFFINENSIS, new species. 

 (Plate XIV, tigs. 11-13.) 



This small species of Cyrtoceras has the general aspect of C. manito- 

 hense, and for a time was regarded as the young of that species, yet a 

 comparison shows that C. baffinensis has a somewhat smaller apical 

 angle. The diagnostic feature, however, is in the depth of the air 

 chambers. These are much more shallow and do not increase in depth 

 with growth nearly as rapidly as in G. manitohense, there being twenty- 

 two of these in 25 mm,, while in the latter species at a similar stage of 

 growth there are about sixteen. 



Collector.— A. H. White. Cat. No. 28198, U.S.N.M. 



Family ONCOOERATID^. 

 CLINOCERAS EXIGUUM (Billings). 



Cyrtoceras exigimm Billings, Can. Nat. and GeoL, V, 1860, p. 172, figs. 17, 18. 

 Oncoceras exigimm Clarke, Geol. Minn., Ill, Pt. 2, 1897, p. 798, pi. lviii, 

 figs. 10, 11. 



In this collection there are five specimens of this species, three of 

 which preserve more or less of the body chamber, and permit a recon- 

 struction of the form of the shell. The body chamber was not less than 

 15 mm. in length and the entire shell not less than 58 mm. Billings gives 

 the probable length as about 50 mm., which is very close to the protrac- 

 tion based on Arctic material, Clarke writes that the Minnesota speci- 

 mens probably did not exceed 30 mm., but as his specimens are very 

 small fragments, this estimate is probably short of the actual length. 

 The first twelve septa back of the living chamber occupy 22 mm., and in 

 another specimen there are nine in 19 mm. The depth of the air 

 chambers decreases very little toward the apex, the average being a 

 little less than 2 mm. down to where the shell has a diameter of 3.5 mm. 



Specimens from shale are usually compressed, and this is the condi- 

 tion of the Arctic material, but the shell was circular in outline, with 

 a very small central siphuncle. 



This species is related to Oncoceras mumkeformis Whitfield, which 

 Clarke referred to Glinoceras. The Arctic material shows the shell to 

 be gently arcuate and to possess the other generic characters of Glino- 

 ceras. Billings's species should be referred to Maschke's genus. * 



Collectors.-^. N. Carpendcr and A. H. White. Cat. No. 28199, 

 LT,S,N.M. 



