OF THE BIDDULPHIE^. 



847 



by alternate angles, forming zigzag 

 chains. Between the two processes, and 

 in a plane at right angles to that con- 

 taining them, are placed two long horn- 

 like processes. Two frustules are often 

 connected by an external decussately 

 punctate cell, as in Isthmia and Bid- 

 dulphia." The processes do not exactly 

 correspond with the angles, but are situ- 

 ated a little to the side in opposite di- 

 rections. This species, beautifully figured 

 in Professor Smith's excellent work, is 

 easily recognized by its broad, truncated 

 processes, (vi. 8.) 



C. Smithii ( Ra.). — Valves in front view 

 turgid ; processes conic, alternating with 

 subidate hom-like spines ; lateral valves 

 orbicular ; cellules distinct. = Eupoclisciis 

 racliatus ?, SBD. i. p. 24, pi. 30. f. 255 

 (not Bailey) ; Biddulpliia radiata, Ro 

 TMS. vii. p. 19, pi. 2. f. 27-29. Thames. 

 The orbicular form and diiferently shaped 

 processes distinguish this species from 

 the preceding. The cellules are not 

 radiant ; and as Professor Smith's name 

 was bestowed in error, and is liable to 

 mislead, we have thought it advisable to 

 change it. 



C. Icevis (E.). — Frustules large, qua- 

 drangular, with short, broad, truncate 

 processes and straight intermediate mar- 

 gin ; valves suborbicular, obscm*ely punc- 

 tate, with two minute, opposite, subme- 

 dian spines. = Biddulphia Icevis, EB. 184.3, 

 p. 122 5 Ro MJ. ^-ii. p. 18, pi. 2. f. 24-26 ; 



Odontella polymorpha, KB. 1844, pi. 29. 

 f 90; Isthmia polymorpha, Montague. 

 Shores of North and South America. 

 (YI. 7.) 



C. theri7ialis (Me.). — Large, joints cy- 

 lindrical, angularly concatenated by a 

 lateral isthmion ; lateral valves A^ery 

 smooth. = Melosira (Pienrosira) thermalis, 

 Menegh. 'On the Animal Nature of 

 Diat.,' p. 391. Warm springs of Eugania. 

 Length of frustules very variable. Kiitz- 

 ing refers this to the preceding species, 

 — a decision from which Meneghini dis- 

 sents. The following extracts are taken 

 from the work of the latter : — " Kiitzing 

 says, ' Your Melosira (Fleurosira) ther- 

 malis is in no respects different from the 

 Odontella polymor2)ha. I have compared 

 your specimen with that of Montague. 

 There are even found the delicate points 

 upon the shield, as in the other, which I 

 have inadvertently omitted in my figure. 

 Your specimen is certainly an Odontella, 

 although the articulations are cylindri- 

 cal.' " On this opinion Meneghini makes 

 the following comments: — "Although 

 I have had an opportunity of examining 

 fi-agments only of Montague's Isthmia 

 polymorpha, I am positive in treating 

 the matter differently. It is admirably 

 figured by Kiitzing ; the articulations are 

 not cylindrical, and, though obtuse and 

 slightly prominent, the lateral processes 

 are very evident." For other distinctions 

 between them, see the work quoted, p. 483. 



Genus BIDDULPHIA (Gray). — Fnistules compressed, quadrilateral, 

 cohering by their alternate angles, and thus forming a zigzag chain ; angles 

 equal, elongated into tooth-like projections ; spines none, or confined to the 

 intermediate rounded projections ; lateral valves constricted laterally at their 

 base. Great difference of opinion exists as to the proper arrangement of the 

 forms here associated, whether they should be included in a single genus or 

 not. Ehrenberg and Kiitzing distribute them in two genera ; but although 

 their genera appear identical, yet their definitions differ so much as to make 

 the agreement in fact merely nominal. Professor Smith unites Cerataulus and 

 Zygoceros, as well as Odontella, to Biddulphia, whilst Professor Bailey, whose 

 opportunities of studpng this family have been so ample, admits the propriety 

 of conjoining Biddulphia and Odontella, but is not prepared to add Zygoceros. 

 Brebisson, who first conjoined Biddulphia and Odontella, subsequently recog- 

 nized both genera. Ehrenberg and Kiitzing concur in describing Biddulphia 

 and Odontella (DenticeUa, E.) as concatenate, and Zygoceros and Hemiaulus 

 as simple. Ehrenberg distinguishes Biddulphia from Odontella by the ab- 

 sence of spines, which are present in the latter. Kiitzing, on the other hand, 

 characterizes Odontella as smooth (not cellulose, though often pimctate or 

 granulate), without internal septa, and Biddulphia as regularly punctato- 

 cellulose, with internal septa. Smith finds spines in the typical species of 

 Biddulphia ; and Baile}^ considers the presence or absence of spines an unim- 

 portant accident. We retain our former opinion, that we cannot exclude any 



