NARRATIVE OF THE CRUISE. 323 



The Petrels. — A large collection of these birds, obtained for the most part in the 

 Southern Ocean, was handed to the late Professor Garrod for anatomical examination, 

 and on his death was transferred to. the late Mr. W. A. Forbes, who made an 

 exhaustive report upon their structure and affinities. The following paragraphs 

 contain his most important conclusions : — " The propriety of the division of the 

 entire order Tubinares into two main families, which must be termed the 

 Oceanitidae and Procellariidae, 1 first proposed by Professor Garrod in 1873, has 

 been fully borne out by my further investigations into the structure of these 

 forms. To the differences in their myological formulae, and in the presence or 

 absence of caeca, may now be added numerous other points, both external and 

 internal. 



" The Oceanitidae agree together in having the following peculiarities which 

 are not shared in — with one or two exceptions marked by an* — by any of the 

 Procellariidae : — 



" The number of secondary remiges is never more than ten. The tarsi are not 

 uniformly reticulate, but are either ochreate, or covered by large transversely-oblique 

 scutes anteriorly. The claws are very flat, depressed, and lamellar. There are no colic 

 caeca* (absent in Halocyptena only of the Procellariidae). There is a peculiar expansor 

 secundariorum muscle. The tendon of the tensor patagii brevis is quite simple 

 throughout. The semi-tendinosus muscle has a well-developed accessory head. The 

 ambiens muscle, when present, does not pass over the knee, but is lost on the cnemial 

 process of the tibia. The number of cervico-dorsal vertebrae is twenty-one. The 

 clavicles have a long, curved, symphysial process. The leg bones are longer than the 

 wing bones. The tarsus is longer than the mid-toe* and ulna, and at least twice as long 

 as the femur. The tibia is at least twice as long as the humerus, and much longer 

 than the manus. The basal phalanx of the middle toe is as long as, or longer than, the 

 next two taken together. 



" The Oceanitidae also agree together in having no basipterygoid processes, no uncinate 

 bone, a peculiarly short and stout humerus, radius, and ulna, a single circular nasal 

 aperture, a sternum with its posterior margin quite or nearly entire, a larger gluteus 

 primus, as well as in numerous other smaller details already noticed. All these 

 characters never coexist together in any Procellarian form, and, if my observations are 

 correct, the Oceanitidae further differ from the Procellariidae by having a biceps brachii 

 muscle of the normal form, with no patagial slip. 



" The Procellariidae, on the other hand, have the following characters : — ■ 

 " The number of secondary remiges is never less than thirteen, and is usually much 

 greater. The tarsi are pretty uniformly covered with small hexagonal scutelke. The claws 



1 Cf. Proc. Zool. Soc. Lond., p. 737, 1881. 



