PERCHERS—PETREL 707 
genus, if Pygoscelis (JOHNNY) be not recognized, but they seem no 
further to require remark. Hudyptes, containing the crested 
Penguins (known to sailors as Rock-hoppers or MACCARONIS), would 
appear to have five species, and Spheniscus (JACKASS) four, among 
which S. demersus, the well-known ‘‘ Cape Penguin,” and S. mendiculus, 
which occurs in the Galapagos, and therefore has the most northerly 
range of the whole group, alone need notice here.! 
PERCHERS, the rendering by popular writers of the word 
INSESSORES, now almost wholly abandoned by systematists. 
PEREGRINE (Lat. peregrinus, wandering) an adjective often 
mistaken for a substantive, and used as an abbreviation of 
Peregrine FALCON, an expression that originally meant one of 
foreign origin, regardless of the species. 
PERISTEROMORPH A, according to Prof. Huxley’s taxonomy 
(Proc. Zool. Soc. 1867, pp. 459, 460), the sixth group of ScHIZo- 
GNATH, consisting of the Columbe (DOVE, PIGEON), but not to be 
confounded with his 
PERISTEROPODES, a section of ALECTOROMORPH4 established 
the year after (op. cit. 1868, p. 296), composed of the CURASSOWS 
and MEGAPODES, being so called from the Pigeon-like structure of 
their feet, in which the hallux is long and on a level with the 
other toes, instead of being short and raised as in the other section, 
Alectoropodes, and it was a consideration of this difference that led 
to his important conclusions in regard to the GEOGRAPHICAL 
DISTRIBUTION of Mammals and Birds before mentioned (page 313). 
PERITONEUM, a thin layer of connective tissue lining the 
whole of the body-cavity, and enveloping the viscera, as well as 
attaching the intestinal folds to each other and to the vertebral 
column as MESENTERY. 
PETREL, the name applied in a general way to a group of 
Birds (of which more than 100 species are recognized) from the 
habit which some of them possess of apparently walking on the 
surface of the water as the apostle St. Peter (of whose name the 
word is a diminutive form) is recorded (Matt. xiv. 29) to have 
done. For a long while the Petrels were ranked as a Family, under 
the name of Procellariidx,? and thought to be either very nearly 
allied to the Laridx (GULL), or intermediate between that Family 
and the STEGANOPODES ; but this opinion has gradually given way, 
1 The generic and specific distribution of the Penguins is the subject of an 
excellent essay by Prof. Alphonse Milne-Edwards in the Annales des Sciences 
Natwrelles for 1880 (vol. ix. art. 9, pp. 23-81), of which there is a German trans- 
lation in the Mittheilwngen of the Ornithological Union of Vienna for 1883 (pp. 
179-186, 210-222, 238-241). 
2 Most commonly but erroneously spelt Procellaridz. 
