230 CHARLES W. JOHNSON. 



Sackeii's Catalogue, is thirty-nine (ten from Mexico). Bigot has 

 since described six, making a total of forty-five species. Macquart's 

 S. fiavipes, 8. puchella and S. vicina, I can only I'efer to Odo)itom;/ia 

 flavkornk Oliv. This synonymy has been caused by the unusual 

 length of the first antennal joint, and in the great difference between 

 the male and female. Loew's S. aiigulari'^, S. marginal^ and S. 

 nigrlveiitris, are undoubtedly the same as S. meigenii Wied. Loew's 

 *S'. liotata and S. qnadrigemma are only color varieties of *S'. iionnula 

 Loew. S. lativentris and S. obesa Loew, are synonyms. 



S. insignis is the S of S. maculosa Loew (Osten Sacken, AVestern 

 Diptera, 203). 



*S'. Uneata Macq. I refer doubtfully to 8. meigenii. Of Walker's 

 species S. badins, being positively identified, has priority over S. 

 picvpes Loew. 



S. mjmpJm I refer doubtfully to *S'. hdicepA Loew, the other five 

 (three Mexican) remain unidentified. For a want of material none 

 of the Mexican species (except 8. mutubiUs Fabr.) have been identi- 

 fied ; but, as they should be studied conjointly, I have added, for 

 convenience, a description of all the species. 



Of Bigot's species 8. deiitata 9 and 8. lacerta Z are unquestion- 

 ably 8. macnlom, Lw. 8. diademata and 8. calopus equals 8. bar- 

 bata Lw. A very black species from Weber Lake, California, I 

 refer to 8. nevadce. 8. simplex remains unidentified. 



In the following table I have only included those Mexican species 

 that from the descriptions seem undoubtedly distinct. 



1. — Head of '^ 9 uarrower than the thorax 2. 



Head of 'J, 9 wider than the thorax 8. 



2.— Eyes of "J, 9 glabrous 3. 



Eyes of % pubescent 13. 



3. — AntennsE ; third joint but slightly flattened 4. 



Antennse ; third joint greatly flattened and suhlanceolate 14. 



4. — Abdominal spots usually connected oji the fourth segment of the male, and 

 always connected on the fourth and usually on the third segment of the 



female 5. 



Abdominal spots never connected on the fourth segmi'ut of the % and rai'ely 



connected in the 9 barbata Lw. 



5. — Fifth segment with a large keystone-shaped marking. iiieIaiiOst<nua Lw. 

 Fifth segment with a dorsal line and spot at the anterior angle. 



lativentris Lw. 

 ti.— Abdomen; lateral triangular markings on the second and third segments, 



widely connected at the lateral margin Briiiieri n. sp. 



Abdomen; latei'al subtriangular markings on the second and third segments 

 not connected at the lateral margins laticepiS Lw. 



