330 



COXTRTBUTTONS FROM I'lTE NATTOMAT. HKIiBAIUUM 



CAiiXika at Ptaiion ;5G()7, itself an ar(ti<: dred^ang, is aiiotlior illustration uf the value of 

 the diatouis fur fixiu^^ tlie source of the materiul coiuposin;^ sea buLtoms. 

 P'ound at .stations 3G()7, -1516II, IJeriuL,^ Sea and off Lower California. 



Cocconeis dirupta Creg. Trans. Roy. Soe. Ediiib. 21: 491. pi. l.f. 25. 1857. Jan. 



Abh. Sehles, Ges. Vaterls. Cult. 1862-: 3. j>l 2B.f. 14. lSfi2. Grun. in Feuzl, 



Reise Xovara ]5ol. 1: II. 1870. Cleve in Nordensk. Ve<,^a Exped. 3: 460. ISS3. 



II. L. Smith, Sp. Diat. Typ. no. 633. 1874. Van Ileur. Syuop. pi ^U.f, IJ 15. 



188t. Schnudt, Atlas pL 196,/, 7, 17, IS, 1804, DoToni, Syll. AIlt- 2: 453. 18i)!. 

 Coceor^ns diaphana \\\ Smith, Synop. lirit. Diat. 1: 22. pL SO. f. 254B. 1853. 

 Coccomis bdtmnjcri Jan.; Schmidt, Atlas pi, 196. f, 22-2S. 1894. 

 Coccomis ddlcala Schmidt, Atlas pj. 196. f, 24^ 1894. 



Cleve" unites under the above name, in addition to those here given^ all cases of his 

 oAvn Cdccipiens ^> which are similar to the above in the broadly oval character of the 

 valves, in the fineness and curvature of the beading, in the presence of a transverse 

 stauros at the middle of the lower valve, and in a general tendency toward a sigmoid 

 outline in the median line of one or b<4h valves. There is mucl) in i<\\uT nf Uus, for 

 (\dirupta does show th.ese characters, even the sigmoid curvature in some instances. 

 I>iit such unification is here attende(! with confusion. The ft^rms thus grouped are 

 too diverse, e. g., C> hdtmnjm Jan., a very evident variety of C. dimpfa and C. sparsi- 

 pimctaia Temp. & Brum, a very evident variety of (\ dccipinis. To call thesetwo one 

 species is carrying condensation too far for practical use. 1 have ar^cordingly united 

 only the three above names with ('.dirupta and have grouped all the other forms under 

 C.dicipifns. This arrangement, tliough no less artificial than that of (Mev(», is no more 

 so, and it affords an easy means of grouping these confusing forms. The salient eliar- 

 acteristic of C. dirupta is, as its name indicates, a hyaline median area on one or both 

 valves, broad at the center and tapering to a point at eadi end, slightly or not at all 

 sigmoid. This line in C. dfcipirn^ is slightly or extremely sigmoid, the ends of the 

 raphe curved like an ''S" in opposite directions, the median area generally narrow or 

 sometimes wanting, and the transverse staiiros plain. Tt may l>e adde<l that the 

 members of the C. dirupta group are generally mufh smaller than those belonging to 

 C. dfcipi<:ns. 



Grunow ^ makes this a variotvof C. snitellitni Ehrenb., for which there is some war- 



rant. As there is, howcvf^-, quite a di ff(M'ence betw(*en what T conceive to be Gregory's 

 typo and that of Elnenberg, I have retained the above name. The two figures of 

 Gregory*s in tlie above citations are not at all alike*. The first was evidently incor- 

 rectly drawn by Tuffen West, so far aa the beading is concerned. It is n^presented in 

 very regular rows evenly graded from the large marginal Ix^ads (o tlie smaller medium 

 ones. But Gregory saysj^ 'Tina beautiful form is at ojic*' charact«Ti/ed by the eqnal 



size of iIh' dots or granules and their great <listance from ea<li other, so that it almost 

 loses th(^ aspect of striation." The faidty n*i)resentalion of this is corrected, iti fact 

 over-<*orrected, in Gregory's second figure, When the type id<*aof Gr(*gory*s species is 

 thus made out and \< compared witli ElirenbtM'g's original ligure and ch^scTiption/ it 

 seems to mo the two are sufficiently Avide apart to admit of the retention of botb names. 

 Found at station 4505II, Santa Cruz light-hous(^, ^^onterey Bay. Cal. 



'^ Sv. Vet. Aka<l. Ilandl. 27'=: 175. 1805. 



b Bib. Sv. Vet. Akad. Ilandl. 1^^: 14. pJ. I,f, 6. 1873. . 



•Eenzl, Reise Xovara Bot. 1: 9. 1870. 



rfOi>. cil. 39. 



^Elnenb. Infus. 194. pJ. 14- f. S. 1838. 



