396 



SCIENCE. 



[Vol. VII., No. 169 



I shall note with interest any future germinations as 

 lengthening the possible dormant period of these 

 seed. 



On April 19 I observed five more germinations, 

 with the characteristics of those mentioned as grow- 

 ing this year. Up to April 24, three other young 

 plants had started, making thirteen since Christmas ; 

 and these are as vigorous as those that started iu 

 1884, — much more so than the growth of the sum- 

 mer of 1885. Geo. F. Waters. 



8 Beacon Street, Boston, Mass., 

 April 24. 



Eskimo building-snow. 



In Science for April 23, 1886 (p. 372), Sergt. T. W. 

 Sherwood has an inquiry about a certain formation 

 of snow. I refer you to a paragraph in Science for 

 April 25, 1884, p. 822, concerning ' ice-banners,' 

 from observations of my own. 



Gilbert Thompson. 



U. S. geol. surv., April 23. 



Certain homologous muscles. 



The writer, having devoted some time of late to a 

 comparative study of the myology of American 

 mammals, has noted several interesting facts, to one 

 of which attention is here asked. 



The myology of the shoulder is, perhaps, more in- 

 teresting than that of any other region, inasmuch as 

 the variations in structure can usually be readily 

 correlated with corresponding variations in habit. 

 This is true in particular when applied to those 

 changes observed in members of the same genus and 

 family. In a forthcoming work I hope to present a 

 mass of details illustrating the nature of these 

 variations. 



The muscular system is so plastic, and so im- 

 mediate an expression of function, that it was hard- 

 ly expected that many hints bearing on phylogeny 

 could be derived from that source. Osteology, pos- 

 sessing as it does so many advantages in this respect, 

 has been trusted far too exclusively, as I hope to 

 show : at least, a careful study of the anatomy of 

 the soft parts may be expected to furnish much con- 

 firmatory evidence. In the case of the shoulder, 

 the omo-hyoid muscle may be said to furnish a valu- 

 able criterion by which to determine the primitive 

 character of a species. Its presence in the archaic 

 types, and frequent absence in specialized forms, can 

 hardly be correlated with change in function. 



The sciurimorphs are a very compact group, and 

 y^t present a great variety of modifications in 

 adaptation to variation in habit. Among the mem- 

 bers of the group found in the United States, the 

 woodchuck (Arctomys monax) is perhaps entitled to 

 rank as the most primitive form. This conception is 

 suggested by the osseous structure, and finds an 

 interesting support in a number of points in the 

 myology, only two of which are here mentioned. 

 The omo hyoid passing from the sterno-hyoid to the 

 anterior margin of the clavicle is very well developed. 

 A very important part of the skin-muscle forming 

 the covering of the cheek is derived from a broad, 

 flat band springing from the anterior third of the 

 sternum, the insertion being in the skin of the lips 

 and chin. But most curious of all is the presence 

 of a well-developed skin-muscle springing from the 

 lower posterior free margin of the rhomboideus 



dorsalis, which, unlike the cucullarius, has an origin 

 far down the back, overlapping the latissimus. The 

 thin band of which mention is made is entirely dis- 

 tinct from any portion of the paniculus until it 

 reaches the region of the cheek, where its fibres ap- 

 pear to lose themselves upon the skin. What gives 

 these points interest is the fact that the only other 

 rodent yet encountered, which has such a muscle, is 

 Geomys, the pouched gopher. In G. bursarius an 

 exactly similar muscle springs from the latissimus at 

 almost the identical point, and has exactly the same 

 course, its insertion being on the pouch, whence I 

 have elsewhere termed it retractor bursae. 



In none of the myomorphs examined has such a 

 muscle been encountered. Without going into further 

 detail, it will be sufficient to point out the fact that 

 there may here be a hint of the antiquity, if not 

 consanguinity, of these types, unless, indeed, it can 

 be shown that an underground habit has developed in 

 one case, — that which has its apparent explanation in 

 the function dependent on the possession of a pouch 

 in the other. 



In the chipmunk, which is pouched, though only 

 imperfectly fossorial and more perfectly sciurine, 

 this muscle is absent. The spermophiles, although 

 the nearest living American allies of Arctomys, do 

 not possess this muscle. In the flying squirrel there 

 is a thin band of muscle passing from the wrist, 

 having its origin on the carpus opposite the volar 

 spur, and passing to the same point as the muscle 

 here described. The flying- squirrel also has a dis- 

 tinct omo-hyoid. C. L. Herrick. 



Dennison university, April 12. 



A means of distinguishing the Canada lynx 

 from the Bay lynx. 



If a dozen zoologists were asked how many species 

 of lynx exist, the majority would probably decline 

 to commit themselves to any opinion, while among 

 the rest would be found advocates for a varying 

 number of species, — as few as one, perhaps, or as 

 many as eight or nine. 



While examining a series of sixty or seventy 

 skulls of American lynxes recently, I hit upon two 

 characters which will, I believe, prove useful in 

 distinguishing between the species more satisfactorily 

 than has been possible hitherto. I found that in all 

 the skulls from far north, indeed in all that were 

 labelled ' L. canadensis,' the anterior condyloid 

 foramen is large, looks downward, and is not 

 confluent with the foramen lacerum posterium ; and 

 that the visible portion of the presphenoid is flask- 

 shaped, the convexity being in front. In all the 

 skulls of L. rufus, maculatus, and fasciatus, on the 

 contrary, the two foramina are confluent, as in the 

 cats generally, and the visible portion of the 

 presphenoid is sagittate or linear. 



The single skull of Lynx borealis in the national 

 collection, and one of L. cervaria, exhibit the charac- 

 teristics of L. canadensis. 



It would appear that in the case of the American 

 lynxes we are dealing with two distinct species 

 only : 1°, L. canadensis ; and, 2°, L. rufus, with its 

 varieties fasciatus and maculatus. It is also proba- 

 1>1< t hat the confluence of the condyloid and lacerated 

 foramina cannot hereafter be regarded as a dis- 

 tinguishing character of the Aeluroidea. 



Frederick True. 



Washington, April 20. 



