186 SOME POINTS IN THE ANATOMY OF STEATORNIS. 
the Strigides, whilst in the Caprimulgide it is more developed, reach- 
ing the lower margin of that bone. 
The tensor patagti brevis—a muscle very constant in its insertion in 
the different families of birds, which arises mainly from: the superior 
extremity of the furcula on each side, and is inserted, after running in 
the patagial fold parallel to the humerus, into the outside of the fore- 
arm, near the elbow—in Steatornis agrees entirely with that of many 
of the Strigide, and differs slightly from that of the Caprimulgide, as 
may be seen from the accompanying drawings (fig. 4, p. 185), where, 
in the former, the main tendon becomes attached to the extensor carpi 
radialis longus directly, whilst in the latter it joins a second more 
superficial tendinous slip which runs back to the outside of the elbow, 
much as in the Passeres. 
By placing the above-mentioned facts in a tabular form, the com- 
parison between Steatornis and its allies will be more clearly seen. 
Steatornis. Strigide. - Caprimulgide. 
Number of carotids....... “2 2 2 
Ambiens muscle..........| Absent........ | Absent.........| Absent. 
Semitendinosus muscle....| Present, with ac-| Absent.. ..| Present, with ac- 
cessory head... cessory head. 
Femoro-caudal-muscle ....| Absent......... Present Goal Present. 
Pectoralis secundus muscle. | Short .......... Short . . | Long. 
The semitendinosus is a muscle very constantly present in birds, 
being absent only in the Owls, Eagles, true Vultures, Humming-birds, 
and Swifts; consequently its presence in Steatornis is in favour of its 
being related to the Caprimulgide rather than to the Strigide. 
In endeavouring, from the facts recorded above, to form a correct 
notion as to the exact systematic position of Steatornis, the difficulties 
in the way are considerable. That it forms a family by itself there is 
little or no doubt, as it presents pterylographical and internal pecu- 
liarities found in no other birds. By a process of exclusion, an 
approximate idea of its position may be formed. The Strigide, 
Caprimulgide, Coraciide, Momotide, Galbulidw, and Steatornithide 
all agree in possessing the following characters—two carotids, well- 
developed cxca, a nude oil-gland, and no ambiens muscle. Among 
these, the Strigide differ from all the rest and resemble the Eagles, in 
having no semitendinosus; and the Steatornithide are equally pecu- 
liar in haying no femoro-caudal muscle. In its pterylosis, as shown 
above, Steatornis resembles the Strigide much more than any of the 
allied families, except that there are only ten rectrices. I have not 
dissected Podargus; but it agrees so closely with Caprimulgus in its 
pterylosis, according to Nitzsch, that it most probably must be included 
