1889.] MR. W. K. PARKER ON STEATORNIS CARtPENSIS. 177 



the 13th sacral is identified as such by its close union (ankylosis) 

 with the postero-siiperior angles of the post-ilia ; its centrum is 

 distinct from that of the 12th. 



Here, in this manifestly archaic bird we have, as in the Parrot 

 tribe, a marvellous variety in the articulations and functions of the 

 vertebral centra. 



The atlas is procoelons, and its joint, behind, with the axis, 

 is flat, with a joint-cavity. The joint-cavity, with a perforated 

 meniscus and a suspensory ligament, is seen up to the sacrum ; but 

 the cervicals, only, are cylindroidal ; the dorsals are opisthoccelous. 

 Then the sacrals are ankylosed, and behind these come the caudals ; 

 which, in front, are subconcave on both faces, and are united by 

 fibro-tartilage without a joint-cavity ; whilst in the hinder part of 

 the series that cavity reappears in a proccelous joint. 



IV. The Sternum and Shoulder-girdle. 



The sternum (Plate XVIII. figs. 7, 8) belongs to the same type 

 as that of Caprimulgus on the one hand, and Suceros on the other, 

 but is most like that of the latter. Like the pelvis it is short and 

 broad, and it has only two notches ; they are wide and rounded, 

 and the xiphoids are all three finished behind by a large rounded 

 plate of cartilage. The whole structure is light and rather feeble, 

 and the bone is pneumatic. The coracoid grooves nearly meet ; they 

 form together little more than a right angle ; between them there is a 

 short, blunt, inferior rostrum (r.st.), scooped above and carinate below. 

 Together, the ^re-costal process (pep.) and the costal edge form a 

 high, nearly equilateral triangle ; there are four transverse condyles for 

 the sternal ribs ; the first of these only leaves a pre-costal tract 3"5 

 millim. in extent. The body of the bone is deep and the keel large, 

 with its fore margin at a right angle with the bodj' ; in front, the 

 keel projects a little at its lower third, where the lesser pectoral muscle 

 ends behind ; it ends 4 millim. in front of the ossified part, and 

 about 13 millim. from the end of the middle metasternal cartilage 

 (middle xiphoid). The whole structure, shoulder-girdle and ster- 

 num, is much like that of the Barn-Owl (Strix flammea), with its 

 single notch right and left behind, the inner notches being nearly 

 obsolete ; that bird also has similar long scapulae and coracoids, 

 and the furcula are not unlike. 



This peculiar isomorphism with the Owl is manifestly adaptive ; 

 I question if this bird is nearer akin to an Owl than it is to a Cor- 

 morant. 



The structure of the sternum is in great contrast to that of the 

 Common Goatsucker ; in respect of its general finish it is more 

 archaic. The comparative measurements are as follows : — 



The notches in Steatornis measure 9 millim. axially and 15 



