MADEIRAN COLEOPTERA. oT 
the straightened sides of its posteriorly widened prothorax, and the 
reduced dimensions of its (almost obsolete) series of impressed 
elytral points, will, apart from many other characteristics, readily 
separate it. 
78. Hydroporus confluens*. 
Dytiscus confluens, Fab., Ent. Syst. i. 198 (1792). 
Hyphydrus confluens, Gyll., Ins. Suec. i. 522 (1808). 
Hygrotus confluens, Steph., Ill. Brit. Ent. ii. 47 (1828). 
Hydroporus confluens, Aubé, Hydrocanth. 557 (1838). 
» Woll., Ins. Mad. 87 (1854). 


Inhabits all the islands of the Madeiran Group, except the southern 
Dezerta, on which there is apparently no water for it to exist in. 
Out of 75 specimens which I have examined (one of which is from 
Madeira proper, 25 from Porto Santo, 3 from the Dezerta Grande, 
and 46 from the Ilheo Chao), there is not a single instancéin which 
the anterior portion of the fourth elytral line (so long and con- 
spicuous in European examples generally) is not obsolete. This 
little difference therefore, although slight, must be regarded as a 
strictly geographical one, 
Fam. 3. GYRINIDA. 
Genus 29. GYRINUS. 
Linneeus, Syst. Nat. 11. 567 (1767). 
79. Gyrinus natator**. 
Dytiscus natator, Linn., Fna Suee. 779 (1761). 
Gyrinus natator, Linn., Syst. Nat. 567 (1767). 
, Fab., Ent. Syst. i. 202 (1792). 
, Aubé, Hydrocanth. 664 (1838). 
— ——, Woll., Ins. Mad. 88 (1854). 



Inhabits Madeira proper, and is hitherto unique,—the only spe- 
cimen which I have seen (and which may possibly have been acci- 
dentally introduced from more northern latitudes) having been 
collected by the late Dr. Heinecken. It is now in the British 
Museum. 
