Ptenidium.~\ CLAVICOENIA. 137 



are smooth and shining insects with a harder integument than is found 

 in most of the Trichopterygidas ; the pygidium is always covered, and 

 the sculpture is variolose; eleven species are found in Britain which 

 may be distinguished as follows : 



I. Head and thorax more or less deeply foveolate- 



punctate. 

 i. Sculpture of elytra deeper. 



1. Form narrower and more elongate ; thorax 

 broadest a little before middle ; basal fovese absent 



(habitat on the coast in seaweed or shingle) . . P. PUNCTATr/M, Gyll. 



2. Form broader ; thorax broadest about middle ; 



basal fovese well marked P. KBAATZI, Matth. 



ii. Sculpture of elytra feeble ; thorax broadest behind 



middle ; basal fovese absent or very indistinct . . P. FUSCICOKNE, Er. 



II. Head and thorax almost smooth and impunctate. 

 i. Thorax with four large foveje at base. 



1. Head without large punctures near eyes ; elytra 



punctured in fine rows P. NITIDUM, Heer. 



2. Head with three large punctures near each eye ; 

 elytra almost impunctate ; basal fovese very large 



and deep P. LSVlGATiJitf, Gyll. 



ii. Thorax with four small fovese at base, which are 

 in some cases absent. 



1. Elytra reddish-castaneous. 



A. Thorax strongly contracted just at base, 



forming an angle with the elytra. 



a. Form very broad and turgid ; thorax more 

 narrowed in front ; eyes more prominent ; 



elytra rather deeply punctured .... P. TUHQIDUM, Thorns. 



b. Form narrower and less turgid ; thorax less 

 narrowed in front; elytra more shallowly 



punctured P. FORMICETOKT7M, Kr. 



B. Thorax not contracted at base, forming a 

 continuous outline with elytra, which are much 



dilated ; basal fovese absent P. GUESSNERI, _EV. 



2. Elytra black. 



A. Sides of thorax strongly rounded, broadest 

 between middle and base, much more narrowed 

 in front than behind ; basal foveas absent or 



very minute P. EVANESCENS, Marsh. 



B. Sides of thorax moderately rounded, broadest 



about middle. 



a. Form broader, elytra larger, with large and 



shallow confused punctures P. ATOMAROIDES, Mots. 



b. Form narrower; elytra smaller, with rows 



of rather small and deep punctures ... P. WANKOWIEZII, Matth. 



The species are variable as regards habitat ; some are found in hot- 

 beds, dead leaves, &c., or by sweeping ; others appear to live solely in 

 ants' nests, while one or two are only found on the seashore in seaweed 

 or shingle, and a few occur under bark and in decaying wood. 



P. punctatum, Gyll. (littoralis, Mots., alutacca, Gill.). Elongate- 

 oval, rather narrow, deep black, shining, rather sparingly clothed with 



