or THE GOMPHONEME^. 



887 



* Frustules in lateral view constricted be- 

 neath the apex, appearing urn-shaped. 



t Lateral view with tlie head apiculate 

 or acute. 



GoMPHONEMA coronatum (E.). — Slen- 

 der, with ventricose middle, obcordate 

 apiculate head, and lanceolate base ; front 

 view crested at apex. EM. pi. 6. 1. f. 33. 

 = G. acuminatum jS, SBD. i. p. 79, pi. 28. 

 f. 238 /3. Eiu-ope, America, Asia, Aus- 

 tralia, (xiv. 36.) G. coronatum is di- 

 stingTiished from the allied forms by its 

 inflated basal portion; but the lower 

 inflation is sometimes very obscure, and 

 we believe Professor Smith was justitied 

 in regarding this form as a mere variety 

 of G. acuminatum. 1-480". 



G. laticeps (E.). — Habit of G. corona- 

 tum, but shorter, and head wider than 

 the central inflation. EM. pi. 5. 1. f. 34. 

 America, Asia. Ehrenberg's figm^es have 

 the basal portion linear, not inflated. 

 He gives about fifteen habitats. 



G. Sceptrum (Rab.). — Habit of G. 

 coronatum, but larger and more robust, 

 the middle more inflated and much 

 broader than the obcordate apiculated 

 head ; base stalk-like, not inflated. RabD. 

 p. 60, pi. 8. f. 8. America. 



G. aciwiitiatuni (E.). — Slender, taper- 

 ing below into the stalk-like base, con- 

 stricted above the ventricose middle ; 

 head dilated, acuminate. SBD. i. p. 79, 

 pi. 28. f. 238. = G. trigo7iocephalum, EM. 

 pi. 6. 1. f. 36 j G. appendiculata, Perty KL. 

 p. 204, t. 17. f. 12. Europe, Asia, Africa, 

 America, and Australia, (xin.23.) Differs 

 from the foregoing species by a cuneate 

 or tapering apex. In a variety figured 

 by Professor Smith the constriction is 

 nearly obsolete. 1-860" to 1-430". 



G. Brehissonii (K.). — Slender, narrow, 

 •with a longly attenuated base and a 

 slightly ventricose middle^ separated by 

 a slight constriction from the cimeate, 

 attenuated, somewhat obtuse head. KSA. 

 p. 66. France. Stipes abbreviated or 

 nearly obsolete. Akin to G. acumina- 

 tum, but more slender, more elongated 

 into the stipes-like base, and head and 

 median inflation smaller. 



G. Americanum (E.). — Lateral view 

 with three inflations, separated by two 

 constrictions ; head ovate, subacute. 

 EM. several figui-es. America, Iceland. 

 1-864". 



G. elongatum (S.). — Lateral view \\dth 

 three inflations, the median one greatest ; 

 upper one oblong, with cimeate apex ; 

 lower slender, slight. S. in ANH. 2 ser. 

 XV. p. 6, pi. 1. f. 4.= G. Brehissonii, Greg. 



MJ. ii. pi. 4. f. 18. France, England. 

 1-864". Scarcely distinct from G. Ame- 

 ricanum ', both have the inflated base of 

 G. coronatum, and cuneate head of G. 

 acuminatum. 



2 1 Head rounded, neither acute nor 

 apiculate. 



G. geminatum (A.). — Frustides very 

 large, in front view cuneate, their ter- 

 minal pimcta obsolete ; lateral view in- 

 flated at the middle, constricted above 

 and below, with dilated, rounded ends ; 

 striae distinctly moniliform. SBD. p. 78, 

 pi. 27. f. 2'3o.=Dio?nphaIa ClavaHercidis, 

 EM. pi. 15 a. f. 93. (vii. 60.) On rocks 

 in subalpine streams. Em-ope. This 

 species forms large spongy cushion-like 

 tufts composed of densely matted fila- 

 ments. The frustules are easily recog- 

 nized by their large size, the absence of 

 terminal puncta in the front view, and 

 the conspicuous striae of their lateral 

 valves. The neck is much constricted, 

 and the large head broadly rounded at 

 the end. Kiitzing refers G. Herculeanum 

 (E.) to this species, but, we believe, 

 erroneously. 



G. capitatum (E.). — Lateral view tur- 

 gid at the middle and slightly con- 

 stricted beneath the broadly rounded 

 head ; puncta in front view evident. 

 SBD. p. 80, pi. 28. f. 237. = 6^. turgidum, 

 EM. pi. 2. 2. f. 40 P Europe, Asia. 1-1720" 

 to 1-280". Striated, attenuated at its 

 base ; stipes elongated, dichotomous. 

 Sometimes the constriction, which is 

 less marked than that of the next spe- 

 cies, is nearly obsolete, and the fi'ustules 

 in the lateral view are obovate. 



G. constrictum (E.). — Enteral view 

 ventricose at the middle, with a short 

 neck and broadly roimded head ; puncta 

 at upper end of front view very evident. 

 SBD. pi. 28. f. 236. = 6^. trunccdum, EM. 

 many figiu'es ; G. paradoxum, EM. pi. 9. 1. 

 f. 33, 34 ; G. pohliceforme, K., Ralfs. 

 Forms a brown discoloration on aquatic 

 plants. Common, (x. 187-190.) 1-1720" 

 to 1-280" ; striated, attenuated at its 

 base ; stipes becoming elongated and 

 branched. Distinguished from G. gemi- 

 ncdmn by its much smaller size and 

 distinct puncta in front view. We find 

 this species very variable in the develop- 

 ment of its neck; and sometimes in a 

 yoimg state the constriction is but slight, 

 and the form resembles G. capitatum. 



G. sid)tile (E.). — Slender, lateral view 

 twice constricted 5 head small, obtuse ; 

 neck slender, elongated. EM. several 

 figures. Asia, Africa, America, Lough 



