NATURAL SCIENCES OF PHILADELPHIA. 11 



of the tarsus touching the ground. The Puffins, however, and a few others, 

 stand well on their feet. All the species but one, fly well, with rapid vigorous 

 motion of the wings, in a straight, firm, well-sustained course. AH progress 

 on or under the water with the utmost facility. They are very silent birds; 

 the voice is rough and harsh ; the notes are monotoned. They feed exclusively 

 upon animal substances procured from the water. 



The uniformity of structure which obtains throughout the family has already 

 been mentioned ; the following paragraphs describe this structure in a general 

 way, so far as the details of external form are concerned :* 



The general form is stout, compact and heavy. The body is depressed, flat- 

 tened underneath. The neck is short and thick. The head is large and heavy, 

 usually oval in shape, more or less flattened laterally, more or less drawn out 

 anteriorly, and sloping gradually on all sides to the bill, but sometimes ending 

 abruptly. The plumage about the head is very soft, dense, and short, except 

 those feathers which constitute the peculiar crest or lateral plumes already 

 mentioned. That of the upper parts is very closely imbricated ; that of the 

 lower is very thick, compact, elastic, and otherwise eminently fitted to resist 

 the action of water. -(- 



The bill, though constantly preserving certain characteristics, varies to a 

 remarkable degree in the details of its shape. The broad statement may be 

 made, that no two speciesj of the family have bills identical in shape. So un- 

 ending is the variation in the bill, that in some cases great differences in shape 

 seem of scarcely more than specific consequence, as is especially the case in 

 the genus Shnorhynchus. The bill in the great majority of species is more or 

 less compressed, sometimes excessively so ; it is frequently, however, nearly as 

 wide as high at the base, and more or less subulate. The contour of the bill 

 in many instances deviates from an ordinary standard so much that the shape 

 may almost be called monstrous. A striking peculiarity of the bill in several 

 genera is the presence of supernumerary elements or accessory pieces, taking 

 the form of salient protuberances. These are usually developed on the culmen ; 

 in one instance on the gonys ; in one at the angle of the rictus; in several 

 along the feathered base of the bill. Besides these appendages, there are often 

 found grooves and ridges on the sides of one or both mandibles. The culmen 

 is always more or less convex ; in one instance it is bi-convex. The tomial 

 edges of the mandibles are more or less sinuate; sometimes nearly straight ; 

 usually decurved at the tip, and slightly notched ; in one instance recurved. 

 The rictus is ample. § The mandibular rami approach each other with a very 

 narrow angle, and soon join, producing a long gonys, which is usually nearly 

 straight. One gentis has a very convex gonj-s ; in two others the gonys runs 

 the whole length of the bill, there being no mandibular rami proper. The bill 

 is entirely horny, except in two species, in which a sott membrane overlaps the 

 base of the upper mandible ; and in a third, where a peculiar knob is not 

 strictly corneous. 



Tiie nostrils are basal, lateral, marginal, impervious; usually linear, or nar- 

 rowly oval ; in a feAV instances placed further from the commissural edge of 

 the upper mandible, and nearly circular. The nasal foss<e are usually very 

 evident ; are sometimes hidden by feathers ; at others are wholly wanting. 

 The extension of the feathers into the nasal fossie varies in degree, when it 

 occurs. In just about half the species the nostrils are naked ; these usually 

 have no true nasal fossae. In the other half fossa; occur ; entirely obtected by 

 feathers in three genera ; partially covered in the rest. The significance of 

 these features will receive further attention below. 



* The writer hopes to bring forward, at some future time, a memoir on the anatomy of 

 the family. 



+ Cf. Nitzsch's Pterylography for pterylosis of Utamania tarda. 



lis tVia rin^riuo specifically distinct from U.lroiUf 



g In two genera, in whioh the excessive compression of the bill produces a very con- 

 stricted rictus, its amplification is pi'ovided for by means of a dilatable skin at the angle 

 of the mouth. 



1868.] 



