532 DR. G. E. DOBSON ON THE [June 20, 



of the presence of prehensile organs resembling the sucking-disks of 

 Cephalopoda. On the inferior surface of the thumb, from the base of 

 the first phalanx, and from the sides of the metacarpophalangeal 

 joint, corresponding to the position of the ball of the thumb in other 

 Bats, arises by a short peduncle a circular hollow suctorial disk about 

 one tenth of an inch in diameter (Plate LV. fig. 5, enlarged). On 

 the sole of the foot a similar but considerably smaller disk (fig. 6) is 

 placed, not in the same relative position, however, as on the thumb ; 

 for it covers the metatarsal bones, not the bases of the first pha- 

 langes of the toes. 



In a paper published in the ' Boletin revista de la TJniversidad de 

 Madrid,' by Senor Jimenez de la Espada, a member of the Spanish 

 Expedition to explore the natural productions and physical conditions 

 of South America, the author relates his observations on the habits 

 of this species, and describes the sucking-cups. I have not been able 

 to procure a copy of this paper; but fortunately a full abstract of 

 the part relating to Thyroptera tricolor is given in the ' Zoological 

 Record ' for 18/0, as follows: — 



"The sucking-cups consist of a coriaceous disk; they are little 

 hemispheres, hollow, flexible, and extremely movable, on the first 

 phalanges of the thumbs of the wings and near the heels on the soles 

 of the feet. They were used by the animal to fasten itself to the 

 fingers as it tried to bite, producing the same feeling as a key or 

 thimble when applied to the tongue after sucking out the air. These 

 cups are deep, membranaceous on the edge, fleshy in the centre, those 

 on the wings larger than those on the feet. The muscular arrange- 

 ment is such as to allow the animal to vary the diameter of the 

 organ ; and by their means the animals attached themselves to the 

 sides of the box in which they were kept, although, when sleeping, 

 they suspended themselves by the claws like other Bats." 



With the latter part of the above statement, referring to a mus- 

 cular arrangement in a sucking-disk, I am quite unable to agree. 

 Microscopical sections of the disk made in every direction failed to 

 exhibit the slightest trace of muscular fibre; and I believe that the 

 animal does not possess the power of varying the diameter of the 

 organ by direct muscular agency. Indeed the presence of a mus- 

 cular arrangement in the sucking-disk of Thyroptera tricolor, such 

 as Senor Jimenez de la Espada refers to, would be a most remarkable 

 anomaly ; for this species would possess special muscles of which not 

 the slightest homologue could be found in any other vertebrate ani- 

 mal. But nature does not form complicated organs where simple 

 ones are equally or sufficiently effective. The remarkable sucking- 

 cups of Thyroptera are evidently but highly differentiated conditions 

 of the integuments and superficial fascia of the balls of the thumbs 

 and soles of the feet. This is shown by their position, by their 

 structure, and by the presence in other Bats of analogous conditions 

 of the same parts, which must be also considered homologous. 



In Vespervgo nanus, Ptrs., V. tylopus, Dobson (Plate LV. figs. 

 1 & 3), and especially in V. pachypus, Temm. (fig. 2), the sole of the 

 foot is very broad, slightly concave, and almost circular in outline, so 



