iSSS.] Gc/icral Notes. 32O 



the skeleton of a bird is an iiitciostiiig fact, and it sees its counterpait in 

 the rudimentary limbs in such a lizard as Ophisaurus ventralia. 



While engaged upon dissecting the eyes of adult Ravens {Corviis corax 

 siniiaius), I have always found a firm osseous plate, of an elliptical outline, 

 with a major axis of some 5 or 6 millimetres surrounding the entrance of 

 the optic nerve, on the outer coat of the eye. In a 'Bulletin' which I 

 have in the hands of the Smithsonian Institution for publication, I figure 

 this structure, as well as the rudimentary metatarsal bone, to which I 

 have alhuicil above. — R. W. Shufeldt, Fori Wing-ate, New Mexico. 



Abnormalities in the Ribs of Birds. — Those who have examined many 

 series of skeletons are well aware that the nuiiiber of ribs in any given 

 species is liable to vary, and that an animal may possess a pair more than 

 the normal number for the species, or that in exceptional cases a pair may 

 be wanting. 



The additional pair of ribs usually appears on the first lumbar vetebra, 

 or what would normally be the first, although now ami then a short, st\li- 

 form pair of pleurapophyses inay be present t)n the seventh vetebra of 

 mammals, or in fishes on the e\-occi])itals. 



The greater number of segments in the vertebial Cf)liniin, and the more 

 generalizetl (lie animal, the greater seems the tendency to variation, and 

 in the Urodele Batrachia even the number of dorsal vertel)r;e is extremely 

 inconstant. 



The following list of costal abnormalities, noted in a Cf)mparati\elv 

 small number of skeletons, would seem to show that in birds the rib ele- 

 ment is subject to frequent variations. 



Galeoscoptcs carol i/wnais with but tive pairs of complete ribs, instead of 

 the normal passerine number of six, the abnormality being caused In the 

 lack of a ha-mapophysis on the rib attached to the fifteenth vertebra. 'I'he 

 styliform rili on the fourteenth vertebra was also reduced in size. 



Galeoscop/es caroliiiri/sis with seven pairs of ribs, a hiemapophysis con- 

 necting the ordinarily free rib of the fourteenth vertebra with the ster- 

 num. 



Mclaiioptila glahrirostris. and Clixneola riparia, each with a seventh pair 

 of ribs with attached iKemapophyses on the second vertebra of the 'sacrum.' 



^uiscaliis purpuniis and Sturi/e/Za iiitiona i/eglecta, each Avith an addi- 

 tional pair of short slender ribs, devoid oi h;emapophyses, on the second 

 vertebra of the 'sacrum.' This is a rather curious coincidence, as the two 

 birds are presumably nearly related. It is the more interesting from the 

 fact that among birds the dorsal portion of the rib is the first to be sup- 

 pressed, and instances are numerous — as among Raptores — where a pair 

 of hremapophyses is normally present without the slightest trace of corres- 

 ponding pleurapophyses. An intermediate condition is found in some 

 birds, «.^., Trochilus colubris and Cypselus apus — a complete haimapo- 

 physis supporting a pleurapophysis whose upper moiety is lacking. 



Examination of the large series of sacra of Alca imfennis in the collec- 

 tion of the U. S. National Museum shows that in this bird an extra (ninth) 



