O MEAEA 03 DIAT0MACEJ5 COLLECTED IN THE ISLANDS OF AEEAN. 



107 



Besides the common forms just enumerated, I have found a large 

 number of the rarer species described by Donkin, Gregory, Greville, and 

 Roper — investigators in this department of natural science whose dis- 

 coveries have been made known since the publication of Smyth's " Sy- 

 nopsis of British Diatomacese," namely — 



Amphiprora maxima (Greg.) 

 Amphora sulcata (Roper). 

 „ robusta (Greg.) 

 ,, obtusa (Greg.) 

 „ arenaria (Donkin). 

 Cocconeis pinnata (Greg.) 

 „ pseudo-marginata 



(Greg.) 



„ Grantiana (Grev.) 



,, scutellum, var. 7 



(Roper). 



Campylodiscus simulans (Greg.) 



Coscinodiscus concavus (Greg.) 



Coscinodiscus nitidus (Greg.) 

 Navicula Hennedyi (Greg.) 

 sestiva (Donkin). 

 forcipata (Grev.) 

 hyalina (Donkin). 

 nitida (Greg.) 

 clavata (Greg.) 

 lineata (Donkin). 

 prsetexta (Greg.) 

 maxima (Greg.) 

 Pinnularia pandura, var. elongate 

 (Greg.) 

 , , semiplena (Grev . ) 



As regards the forms included in the foregoing list, I have no remark 

 to make beyond the record of their occurrence, except in the case of 

 Campylodiscus simulans and Coscinodiscus nitidus. Several frustules of 

 Campylodiscus simulans have occurred in the gathering, and in many 

 instances I have observed the same peculiarity which Dr. Gregory 

 noticed in the frustules of Campylodiscus hicruciatus, namely, that 

 the opposite valves are frequently placed at right angles to each 

 other. 



Coscinodiscus nitidus is figured and described by Dr. Gregory, in 

 his paper on " New Forms of Diatomaceae found in the Firth of Clyde," 

 and supposed by him to be the same as a form previously figured from 

 an imperfect specimen found in the Glenshira Sand. In the paper on the 

 Clyde forms Dr. Gregory, having described Coscinodiscus nitidus, proceeds 

 to say : — " This pretty disk was figured, without a name, from an im- 

 perfect specimen in my last paper on the Glenshira Sand.*' Having found 

 it tolerably frequent in Lamlash Bay, T now figure a perfect example, 

 which provisionally I refer to Coscinodiscus." 



This form found in Lamlash Bay occurs frequently in Dr. "Wright's 

 gathering, and with equal frequency is another form very like it at first 

 inspection, but which, on closer examination, presents distinctive cha- 

 racters. This latter appears to me identical with that figured from an 

 imperfect specimen in the paper on the Glenshira Sand. A careful 

 comparison of many frustules seems to confirm this opinion. The Clyde 

 form is accurately described as follows : — " Surface of the disk marked 

 with distant and irregularly radiated lines of rather large, round, distant 



Transactions of the Microscopical Society," vol. v., PI. 1, Fig. 50. 



