274 A. E. Yerrill — North American Cephalopods. 



actual projection anteriorly is but slight, because the translucent 

 edge beyond it rises to about the same level. The lateral-posterior 

 borders of the frontal lamiuiB are sinuous and incurved in the middle; 

 the palatine lamina is broad, with the posterior lateral edges incurved 

 and sinuous. 



The lower mandible has the extreme tip strongly incurved, forming 

 a slight notch, close to the tip, below which the edges are slightly 

 incurved or nearly straight, with a decided V-shaped notch at the 

 base ; the anterior edges, beyond the notch, form a triangular tooth 

 of the inner lamiuiB, but this is obscured, unless viewed by trans- 

 mitted light, by the outer alar laminae, which rises at its anterior 

 edge, which is translucent, nearly to a level with the tooth ; the 

 inner ends of the alae are wider than the middle, and broadly rounded ; 

 the gular laminas are short, narrowed posteriorly, with their inner 

 edges incurved, and with a thickened, prominent ventral carina. 



The jaws of a large specimen measure as follows: upper mandible, 

 tip to posterior end of palatine lamina, 22'""'; to dorsal end of frontal 

 lamina, 16; to posterior lateral edge of same, 9; to base of cutting 

 edge, 5 ; inner edge of palatine lamina to dorsal end of frontal 

 lamina, 17. Lower mandible, tip to inner end of alse, 13"^"^; to ven- 

 tral notch of alse, 4 ; to venti'al notch of gular laminae, 9 ; to posterior 

 end of same, 16 ; to base of cutting edges, 5. 



The buccal mass has, on the outer surface of the dorsal and lateral 

 sides, a broad, thin, brown horny plate, with a notch posteriorly, in 

 the median line. 



The odontophore (Plate XXXVII, tig. 8), is remarkable for the 

 length and sharpness of the teeth, especially of the central and outer 

 rows. The median teeth have a long and very acute median denticle, 

 with much shorter lateral ones. The inner lateral teeth have broad 

 bases and a long and very sharp central denticle, with a much shorter 

 lateral one, on the outside. The next to the outer lateral teeth are 

 simple, slender and sharp. The outer lateral teeth are much longer, 

 strongly curved, and very acute. 



The pen (Plate XXVIII, fig. 4) is long and slender, with a slender 

 midrib and strong marginal ribs ; the anterior end is thin, broad pen- 

 shaped, subacute ; from very near the anterior end it tapers gradu- 

 ally backward to about the posterior fourth, where it becomes very 

 narrow, apparently consisting only of the consolidated lateral ribs 

 and midrib, the former showing on the ventral side a thin groove 

 between them, the latter appearing as a slender ridge on the dorsal 

 side. The posterior portion is narrow-lanceolate in form, with thin 



