182 MR. W. K. PARKER ON STEATORNIS CARIPENSIS. [Apr. 2, 



Steatornis ; and the shape and strength of its leg-bones are in great 

 contrast to what we see in such Fowl-Uke Coccygomorphae as the 

 Musophagidte and the Ground-Cuckoos. 



The femur (/.) of Steatornis is, perhaps, the straiijhtest to be 

 seen in the Class ; the breadth is 8-3 millim. above and below, and 

 it narrows to a diameter of 3*5 millim. in the middle of its shaft. 

 The condyloid ledge for the i&Me fibula (fb.) is not well-marked ; 

 that bone is a little above half the length of the tibia, which latter 

 bone is as straight and primordial as the femur ; it would seem as if 

 these bones had not altered in shape since the middle of incubation. 

 The breadth of the head of the tibia (t.) is 9 millim., across its tarsal 

 base 8 millim., whilst the middle of the shaft is only 3 millim. 



The cnemial ridges are very rudimentary, and the ridge outside 

 for the fibula (/6.) only reaches 15 millim. downwards. 



A thin delicate tendon-bridge exists in front of the base of the 

 tibia below (Plate XX. fig. 4) ; but there is no special depression 

 between the astragalar and calcaneal regions of the condyle, for the 

 intercondyloid knob on the distal tarsal (or head of the shank) is 

 nearly obsolete (Plate XX. fig. 3). The inner part of the condyle 

 is formed by the astragalus, and the outer by the os calcis ; there 

 is a rudiment of the intermedium between them ; the centrale, or 

 "naviculare" {nv.), is seen as a cartilaginous, curved wedge behind 

 the joint. The tarsal outgrowth behind the liead of the shank to 

 form a tendon-canal for the plantar tendons (Plate XX. figs. 3, 5) is 

 open. This part is closed in, and forms one canal in Ceryle alcijon ; 

 in the Martin (Chelidon urbica), as in all the Coracomorphoe, there 

 Rrefve canals in the compound mass ; in the Swift {Cypselus apus) 

 there is an unusual thing — a little bridge in front of the distal tarsal ; 

 but the two ridges behind are not united\ 



There is a notable peculiarity in the structure of the inter-tarsal 

 joint. The condyloid trochlea formed by the astragalus is large and 

 perfect, and rolls in a well-formed concavity on the inner side of the 

 great distal tarsal. But the calcaneal part of the double trochlea is 

 feeble (Plate XX. figs. 3-5) and the outer part of the facet on the 

 lower tarsal is almost flat^. 



The tarso-metatarsus shows the signs of division into three main 

 metatarsals, both above and below, 2nd to 4th (Plate XIX. figs. 4, 5). 

 The free distal piece that carries the " hallux" {mt.t'.) is 5-5 millim. 

 long. 



On the outer side of the head of this smnll shank the 5th meta- 

 tarsal (mt.t. 5) can be seen as a club-shaped rudiment, fused with 



1 The classificatioii of birds by the palate is very useful as a help to other 

 methods, everything else being taken into account. Nowhere does it show its 

 value more than in the Coracomorphre ; they are all " jEgithognatLous " ; but 

 the ^Egithognatha; and the Ooracomcrphse are not equal groups— the former 

 is too large for accurate superposition on the latter ; the Swifts (OypseUdae) are 

 jEgithognatha;, but they are not Coracomorphse. 



^ This obliquity reminds one of that in the free astragalus itself in the Mega- 

 therium, as compared with the same bone in the Horse, the latter having the 

 condyle in two nearly equal, oblique semicircular elevations, whilst in the 

 former the two convexities are extremely unequal. 



