350 MR. R. SHELFORD ON A COLLECTION OF 



4 spines on posterior margin, beneath ; all the spines strong. Formula of 



. , . 2 11 

 apical spines ^, j, ^■ 



Total length (^) 12-5 mm,, (?) 13 mm. ; greatest breadth of abdomen 

 (c?) 4-,5 mm., (?) 5 mm. ; length of tegmina 3'5 mm. ; pronotum 3-2 mm. 

 X 4*5 mm. 



The three specimens are not in a very good state of preservation, and the 

 ventral aspect of the abdomen in the male is obscured at the apex. 



Subfam. NycTiBOEiNiE, 



? Nyctibora succinica, sp. n. 



? . No. 5^25 (larva). 



This is a larval moult in a bad state of preservation, there being a large 

 hole in the dorsal surface. Professor Klebs informs me that the specimen 

 was found under fragments of wood enclosed in amber, and that he has never 

 seen any other specimen like it in all the collections of amhev-inclusa that 

 he has examined. The specimen, though immaturej is far larger than any 

 other species of cockroach known from the amber fauna^ and the adult form 

 must have rivalled in size the modern representatives of the genus. I have 

 already oiven reasons to account for the absence of large species in the amber 

 fauna, and need not repeat them again. 



It is rarely possible to place with absolute certainty any larval cockroach 

 in its correct genus, and the systematic position of this species is open to 

 considerable doubt. The unique specimen has a peculiar polished sheen on 

 the thoracic tergites, and this appearance is due, I believe, to the presence of 

 a minute sericeous pile (such as is highly characteristic of the Nyctiboringe) , 

 in which air is enclosed. Except at the margins of the tergites it is not 

 possible to detect the individual hairs of the sericeous pile even with a high- 

 power lens ; but when an insect is imbedded in a substance, such as amber, 

 with the same refractive index as air, many minute details of sculpture and 

 pilosity are lost, and the latter can only be inferred to be present by the 

 optical effect produced when mechanically combined with air particles. At 

 first I was inclined to place the species in the subfamily Blattinas, but as the 

 specimen is a female and in the structure of the sub-genital lamina exhibits 

 none of the groovings which in larval Blattinse foreshadow the valvular 

 nature of the adult sub-genital lamina, it is certain that my first identification 

 was incorrect. In its structure and facies the specimen agrees well with the 

 characters of the Nyctiboringe. 



The following is a description of the unique specimen: — 

 $ . Piceous, with a silvery sheen on the thoracic tergites. Head damaged 

 and distorted. Antennpe setaceous. Pronotum anteriorly parabolic, poste- 

 riorly truncate, wider than long. Meso- and metanotum with the posterior 



