NATURAL SCIENCES OP PHILADELPHIA. 



165 



(ur, ariel and ? brevirostris, and Prion proper, the following comparison is in- 

 stituted. 



The fringe of laminae is smaller and weaker, and inflected inwards rather 

 than descending vertically ; and it is either restricted to a short space near the 

 base of the b\\Y (turlur, ariel, ? brevirostris) being quite obsolete more anterior- 

 ly; or if as in Banksii it extends to the unguis, it is small, weak and incon- 

 spicuous. The lateral lamellae of the bill have scarcely more of development 

 and inflation than in other genera of Procellariinse, instead of being immensely 

 hypertrophied ; and they have a lateral, vertical aspect, instead of a superior 

 nearly horizontal one. The commissural edge of the upper mandible looks 

 downwards, with little inflation or reflection outwards, and nearly (though not 

 quite except apically) touches the under mandible. There is no groove for 

 the reception of the fringe of the upper mandible; but in its place the ordinary 

 lateral sulcus of the sides of the lower mandible is apparent, though not very 

 strongly marked. The inferior mandibular rami divaricate at an acute angle, 

 and are quite straight, instead of widely diverging with a mutual concavity. 

 The submental space, narrow and triangular instead of broadly conoidal, is 

 quite fully feathered, instead of nearly naked ; and doubtless has little of the 

 distensibility which characterizes that of Prion. The extent of the feathers on 

 the lower mandible is much more restricted. The unguis of the bill is larger, 

 stronger, more convex, its tip more decurved, the chord of its convexity form- 

 ing more instead of less than a third of the length of the culmen. The lateral 

 outline of the bill is straight not convex. The tail is shorter than in Prion, 

 being contained nearly twice in the wing ; and it is less cuneiform, The nos- 

 trils and the proportions of the feet, are as in Prion ; while the entire simi- 

 larity, almost identity, of the coloration has doubtless had much to do with 

 the referring of the species of this genus to Prioo. 



In the following antithetical table the main diagnostic points of the two 

 genera are contrasted. 



c. 



e. 

 / 



PSEUDOPRION. 



Poorly developed, or 

 entirely obsolete to- 

 wards end of bill. 



Normal ; vertical ; not 

 vaulted ; nor with 

 inflated free edge. 



Concave. 



Of ordinary size, its 

 chord more than a 

 third of culmen. 



Straight. 



Absent. 



g. Apparent. 



h. Nearly straight. 



i. Narrowly triangular, 

 well feathered. 



k. Extend nofurtherthan 

 those on culmen. 



I. Moderately graduated, 

 central feathers not 

 protruding; contain- 

 ed nearly twice in 

 the wing. 



Differential Elements. 



a. Fringe of serrations. 



b. Lateral lamellx of bill. 



c. Dorsal outline of cul- 



men. 



d. Unguis. 



Literal outline of bill. 

 Groove for reception of 

 fringe. 

 Lateral groove en lower 

 mandible. 

 h. Cutting edges of lower 



mandible. 

 i. Inter ramal or submental 



space. 

 k. Feathers on lower man- 

 dible. 



1. Tail. 



Phion. 



Extensively and com- 

 pletely developed 

 throughout. 



Hypertrophied ; hori- 

 zontal ; arched ; with 

 inflated free edge. 



Straight. 



Broadly conoidal, near- 

 ly naked. 



Extend much beyond 

 those on culmen. 



Much graduated, cen- 

 tral feathers elonga- 

 ted, contained one 

 and a half times ia 

 the wing. 



1866.] 



