OF WASHINGTON. ,1 



ploration, between 3 and 400 species will be added to our 

 lists. 



As stated above, these semi-tropical thickets occur in isolated 

 patches in the lowest parts of the delta ; wherever the ground is 

 a little more elevated, the usual mesquite and spiny chaparral, 

 liberally interspersed with Opuntias, make their appearance, and 

 with them the general fauna of southwestern Texas. 



To any one coming from the north into this region it becomes 

 at once evident that the Arroyo Colorado, which is the northern 

 most of the old arms of the Rio Grande, forms the northern 

 boundary of the semi-tropical flora and fauna, while, from infor 

 mation received from Prof. Townsend,* they extend up the river 

 to the head of the same arroyo, or, at most, to the town of Ed 

 inburgh (Hidalgo). Toward the coast, the peculiar Yucca- 

 covered ridges form a characteristic feature of the country, and, no 

 doubt, harbor semi-tropical insects. Finally, the maritime fauna 

 of the delta is semi-tropical and probably extends north of the 

 mouth of the Arroyo Colorado as far as Corpus Christi Bay. 

 In what way the semi-tropical fauna is continued southward 

 through the State of Tamaulipas I am unable to state. 



The area thus circumscribed within the political boundaries of 

 the United States is extremely small, in fact much smaller than 

 that occupied by the semi-tropical region of Florida or Baja Cal 

 ifornia. Like the Floridian region, the Texan semi-tropical flora 

 and fauna are doomed to almost complete extinction by the prog 

 ress of agriculture, and already at the time of my visit flourish 

 ing sugar-cane fields and corn-fields covered the major part of 

 the area once occupied by the semi-tropical forest. 



The paper was briefly discussed by Messrs. Gill, Ashmead, 

 Waite, and Howard. Dr. Gill said that Mr. Schwarz's observa 

 tions on the extremely limited character of this fauna in Texas 

 agreed w r ith his own deductions from a study of fishes. Fresh 

 water fishes, he said, were extremely well adapted for faunal dis 

 tribution studies, on account of their necessary restrictions. We 

 have, in the vicinity of Brownsville, our only representatives of 

 certain characteristically tropical families of fishes, namely, Asty- 

 anax and Heros. Mr. Ashmead spoke particularly of the So- 

 noran fauna of southern Texas, and said that, from his examina- 



* See also Dr. V. Havard's paper on the flora of western and southern 

 Texas (Proc. U. S. Nat. Mus., VIII, 1885, p. 449-533). 



