AMERICAN COLEOPTERA. 293 



thorax entirely blue, and the punctuation more regular and not conflu- 

 ent. The elytral vitta is also a constant difference. 

 Occurs in Arizona. 



II. floridana Schwarz. — Above and beneath dark blue, nearly black. 

 Vertex sulcate. Thorax broader than long, sides nearly parallel, coarsely, deeply 

 and somewhat confluently punctured. Elytra with eight rows of coarse punc- 

 tures, the punctures of the four inner rows larger and more elongate than the 

 others, the alternate intervals very slightly more elevated. Lateral margin scarcely 

 visibly serrulate. Length .IS inch ; 4.5 millim. 



The form of the thorax will distinguish this from the following: uni- 

 formly blue species. 



Occurs in Florida. 



M. excavata Oliv. (Pluto Newm.). — Bluish black, moderately shining. 

 Front sulcate. Thorax distinctly wider at base, the disc coarsely and irregularly 

 punctured. Elytra with eight rows of coarse deep punctures, the two inner rows 

 less deep and somewhat confused, the intervals sometimes slightly elevated, 

 usually flat, margin of elytra serrulate. Length .20 inch; 5 millim. 



In this species there is considerable variation of elytral sculpture, so 

 great that I had supposed two distinct forms existed. Certain specimens 

 have the costae slightly indicated and may be considered the typical 

 forms, others again have no trace of costae. A form occurs in Texas 

 without costae, with the rows of punctures quite regular, these approach 

 very closely to a/aiiea. 



Occurs from Canada to Georgia and Texas. 



M. Erebus Newm. — Bluish black, feebly shining. Vertex sulcate. Thorax 

 broader behind, coarsely and deeply cribrate. Elytra with the series of punctures 

 much confused, the punctures very large and somewhat confluent, especially at 

 the sides, margin of elytra serrulate. Length .18-. 2(1 inch; 4.5-5 millim. 



This species carries to the greatest extreme the irregularity of the 

 elytral punctures, as well as their size and depth. It is very rare that 

 any specimen exhibits an entire row of punctures. There being no regu- 

 lar rows of punctures the intervals are consequently never costiform. 



Occurs in Florida. 



HI. cyanea Say.— Bluish black, sometimes slightly bronzed, shining. Ver- 

 tex sulcate. Thorax broader at base, coarsely and deeply punctured. Elytra 

 with eight regular rows of equal punctures, the intervals equal and never cari- 

 nate, margin not serrulate. Length .24 inch; 6 millim. 



Occurs in Missouri, Colorado and Texas. I have seen a specimen 

 marked New York. 



The preceding four species of uniform dark blue color are very puzz- 

 ling and difficult to separate, and with a greater or less amount of mate- 

 rial will give rise to differences of opinion as to whether the number 

 four should be increased or diminished. My first study of the series, 



(74; 



