168 PROCEEDINGS OP THE ACADEMY OP 



Ardeidcc. I have not met with as detailed a description of its peculiarities 

 as seems desirable. 



The culmen, from the extremity of the nasal case to the root of the unguis, 

 is quite straight. Though rising up as a conspicuous ridge between the deep 

 longitudinal sulci on either side, its outline is broad, flat, depressed, and not 

 carinated. The unguis of tbe upper mandible is small and weak, and hardly 

 rises above the level of the culmen proper; its convexity and decurvation are 

 slight. 



On either side of the culmen, from the root of the nasal case to the junction 

 of the lateral mandibular lamellae with the unguis, lies a well-marked, deep 

 longitudinal sulcus ; the central line of which depression, from the end of the 

 nostrils to the unguis, is occupied by a distinctly defined ridge. 



The immensely-developed lateral lamellae of the superior mandible have so 

 great a lateral extension, as to make the width of the bill at its broadest part 

 nearly two-thirds its length. These lamellae are arched and inflated through- 

 out : and their surface is superior, not lateral. The free commissural edge is 

 convex in outline; retreating slightly inwards and backwards from the 

 broadest point of the bill, which is a little in advance of its extreme base ; 

 converging more rapidly and nearly in a straight line thence to the unguis ; it 

 is dilated and bulging posteriorly where it overhangs, but by no means meets 

 or touches, the inferior mandibular rami ; more anteriorly, it is deflected 

 downwards, and terminally rests against the unguis of the lower mandible. 



From the under surface of the lateral lamella near its free edge grow a 

 series of serrated laminae, which extend from the very angle of the mouth to 

 the unguis ; their ou'line corresponding nearly to that of the edge of the 

 lamella whence they spring. They are directed downwards, with a little out- 

 ward and forward inclination. They are longest, largest, and their " set " is 

 most oblique at the broadest point of the bill ; whence, as they proceed either 

 forwards or backwards, they diminish in size and become more vertical in 

 direction. It is this fringe of serrations that is in apposition with the under 

 jaw ; forming, therefore, the true commissural edge of the upper mandible. 

 These laminae are, so to speak, a series of plates, antero-posteriorly thin, 

 elastic and yielding; transversely wide and resisting; whence it results that 

 ihey can readily be bent away from each other ; but the series cannot be 

 laterally deflected, as a whole; exactly as is the case with the teeth of a 

 comb. 



The nasal tubes are very short, measuring hardly more than a fifth the 

 length of the culmen and unguis ; broad and depressed; placed conspicuously 

 hieh upon the base of the culmen. They are somewhat more elevated api- 

 cally than basally ; their apex is so deeply emarginate as to cause a partial 

 segregation of the two tubes towards their termination. The orifice of each 

 naris is circular; the internasal septum rather wide. 



Corresponding with the general shape of the upper, the lower mandible is 

 very broad ; its rami widely divaricating, presenting much concavity towards 

 each other. Its cutting edge is very sharp and strongly sinuate for its whole 

 length, being curved in several planes oblique to each other. From the 

 widest point, which is opposite the extremity of the feathers on its side, the 

 rami rapidly converge to the unguis ; which latter is very small and weak, its 

 gonys very concave in outline, its tip acute and much decurved. There is 

 hardly an eminentia symphysis. 



The true lateral sulcus of the rami, seen in most Procellariinse, is wanting. 

 In its place we have, ju3t external to the true cutting edge of the lower man- 

 dible, a groove which extends the whole length of the ramus; deepest and 

 most marked posteriorly; apically becoming obsolete. This groove, owing 

 to the inflection of the edge of the mandibular ramus, looks upwards and 

 outwards, and into it the fringe of laminae are received. More anteriorly 

 where the groove is obsolete, the teeth simply abut against the side of the 

 under mandible. 



[May, 



