8 PKOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



Bermudians as tbe "split-thumb", from its power of wounding by a 

 sharp appendage of the larger claws, produces a viciously sharp, snap- 

 ping noise, apparently in the same manner with Alpheus. 



The " Bermuda lobster" {PanuUrus americanus M. Edw.) makes a loud 

 grating noise. Mr. Kent describes the voice of the allied species [Pa- 

 Unurus quadricornis) as being produced by the rubbing together of the 

 spinous abdominal segments. In the species observed by me, the sound 

 was produced by means of certain modifications of tbe lower joints of 

 tbe antennae. There is at the base of each antenna, upon the anterior 

 part of the cephalo-thorax, a broad elevated ridge, parallel with the 

 axis of the body, which in an adult of eighteen inches would be about 

 two inches long. The rounded crests of these ridges are closely em- 

 braced by processes from the sides of the basal antennal segments. The 

 profile of each ridge describes the segment of a circle, the centre of 

 which is the centre of articulation of its accompanying antenna. When 

 the antennae are moved forward and backward, their tips waving over 

 tbe back of tbe animal, the close contact of the hard, smooth, chitinous 

 surfaces produces a shrill, harsh stridulation, like the sound of filing a 

 saw. I have never heard the noise when the animals were under water, 

 though I have seen them waving their antennjB. I have no doubt that 

 they can thus produce vibrations perceptible to their mates at great 

 distances, especially if their other senses are as acute as that of smell, 

 which I have tested in a very curious manner. Both sexes are provided 

 with the vocal organs. 



December 2.5. 1877. 



ON A NEW niJinjniivc; bird (atxhis x:i>i.ioti) froiti ouATEmALiA. 

 By ROBERT RIDOWAT. 



Having had occasion, recently, to examine some specimens of Hum- 

 ming Birds, I happened to notice certain striking differences between 

 two examples labelled '•'■Atthis heloisw^^ — one from Guatemala, belonging 

 to Mr. D. G.Elliot, the other a Mexican specimen, in my own collection, 

 obtained from M. Boucard. The differences observed between these 

 were so obvious that I immediately inspected the series contained in 

 the collection of the National Museum, and on comparison found them 

 repeated in the specimens contained therein, including two males from 

 Jalapa and one from the Volcan de Fuego, Guatemala. Tbe former of 

 course represent the true A. heloisw, being from the locality whence tbe 

 types of that species were procured, and with them my Mexican ex- 

 ample agrees in all essential particulars. Both the Guatemalan speci- 

 mens, however, are very different from any of these, and undoubtedly 

 represent a distinct species, which being, so far as I have been able to 

 ascertain, hitherto unnamed, I propose to characterize as follows : — 



