40 PROCEEDINGS OF THE ACADEMY OF 



the day before the reception of the proof of the foregoing paper, and conse- 

 quently too late to compare my views with those of the distinguished author. 

 I am happy to find that the validity of the groups of Viviparida% which have 

 been above denned, is confirmed by the researches of Dr. Troschel, who has 

 examined the dentition of several species of true Viviparus, besides that of the 

 Pahidina subcarinata of Say, for which he has proposed the name Lioplax. The 

 latter name is now substituted for Haldemania of Tryon, and is modified to form 

 the name of a group containing that genus and Melantho. 



Additional Remarks on the North America iEGIOTHI. 

 BY ELLIOTT COUES, A. M., M. D. 



Since the publication in the Proceedings of the Academy for November, 

 1861, of rny Monograph of the genus, the Smithsonian has been constantly in 

 the receipt of additional specimens from all parts of North America. These 

 were mostly the A. linarius ; but collections from the North have usually 

 contained a number of well -characterized examples of A. exilipes. Nothing, 

 however, of special importance has been elucidated, until the reception of a 

 series collected in winter in the vicinity of Quebec. These specimens, as they 

 throw much light on the variations of the typical species of the genus, 

 A. linarius, will merit a brief notice. If the deductions I have drawn from 

 these specimens are warrantable, we have in North America the forms long 

 recognized in Europe as A. HolbSlli and A. rufescens ; and these are both rather 

 races than distinct species. 



Selecting from the series two or three skins which differ most markedly from 

 the usual style of linarius, and comparing them with a typical specimen of the 

 latter from Philadelphia, I find the following differences : 



The bird is very decidedly larger. The difference in total length is nearly 

 one inch, as near as I can judge from the dried skins. The wings and tail are 

 each about a fourth of an inch longer. The tarsus and middle toe with its 

 claw are together about two-tenths of an inch longer.* The bill and feet are 

 decidedly larger and stouter, though perhaps not disproportionately so. The 

 former is somewhat elongated ; its lateral outlines straight instead of a little 

 concave ; its culmen slightly curved. The bill is of a bright chrome-yellow, 

 except just along the culmen and at the extreme tip. The gular spot seems 

 rather large. In other respects, the two birds are quite identical, for, with 

 these differences in size, there is an exactly proportionate increase in the bill, 

 feet, wings and tail ; and the colors of the two do not differ appreciably, ex- 

 cept in the bill, and perhaps the larger gular spot. The specimens give the 

 idea, in fact, of overgrown individuals of the common linarius. 



But now, on examining in detail the rest of the series, I find that, from 

 the one extreme, the characters of which have just been given, there is a com- 

 plete and gradual transition, a diminution in size, down to specimens which 

 cannot possibly be distinguished from typical linarius. There is no break in the 

 series ; no dividing point where we can stop calling the specimens " linarius" 

 to give them another name ; in spite of the discrepancy which is so evident 

 between the two extremes. 



The point of interest which attaches to these specimens, is the bearing they 

 may have on the mooted question of the claims of sEgiothus Holbolli to full 

 specific rank. As was the case at the time of the preparation of my Mono- 

 graph, I have never examined a specimen which professed, upon good Euro- 

 pean authority, to be that species. Careful examination, however, of the 



*The tarsus, middle toe and claw together, of the specimen sunder consideration, measure 

 absolutely 1*20 inches ; the same parts in linarius are about one inch : in exilipes -80 of au 

 inch. 



[Feb. 



