On Diatoms from Chincha Guano. 481 



mandibular barbels with short simple branches ; anterior 

 mandibular teeth very short, 40 to 42. Adipose dorsal 4 

 times as long as deep, 2£ to 3£ times as long as its distance 

 from the rayed dorsal. Humeral process narrow, keeled, 

 sharply pointed. Body covered with granular papillae. Olive 

 above, yellowish beneath ; dorsal, anal, and paired fins black 

 in front, orange behind ; caudal black, edged with orange. 



Total length 230 millim. 



North end of Lake Tanganyika. 



LXV. — Note on Diatoms from Chincha Guano. 

 By C. Meeeschkowsky. 



[Plate XVI.] 



1 haye, through the kindness of Mr. E. Thum, of Leipzig, 

 been provided with a very interesting slide containing a great 

 number of Diatoms from Chincha guano (in Peru). Having 

 carefully studied the various forms which it contains and 

 determined the species so far as possible with the aid of 

 the few books at my disposal, I give in the present note a 

 list of forty-one forms accompanied by a few remarks con- 

 cerning several of them and by the description of some new 

 species and varieties. 



The majority of Diatoms of which the Chincha guano 

 material is composed belong to the group Anaraphidieae or 

 Cryptoraphidieaa. Different kinds of Biddulphia, small species 

 of Coscinodiscus and Chcetoceros, represented by a great 

 number of species, form the greatest bulk of this material. 

 There are only a few representatives of the group Raphidieas 

 and still fewer belonging to the group Pseudoraphidieae, or 

 Bacilloidese, as I propose to call this group *. 



1. Diploneis vacillans, var. delicatula, CI. Very rare. 



2. Navicula Hennedyi, var. subrostrata ; nov. var. (PI. XVI. 



fig. 14.) Very rare. 



Size small, length 0'044 mm., breadth 0"025 mm. : valve 

 elliptic, with slightly rostrate apices ; lateral areas moderately 



* In a note which will soon be published I have separated the Nitzschi- 

 oideae and Surirelloideae from the rest of the Pseudoraphidian Diatoms, 

 and given to the latter the name Bacilloidese, while the former have been 

 united in a new group called Carinata?. 



