ill!Ill

45 2 TERPSINOE.
Fig. 175^. Isthmia enervis.
Valve view.
Valve oval, elliptic, with coarse cells irregularly
hexagonal placed in rows radiating round a group
of central cells ; cells of process diminishing
gradually in size up
to the end. Girdle face
elongated, trapezoidal, with conspicuous process,
valve portion having 1*5 rows of cells in 1 c.d.m.
Connecting membrane with cells in regular
longitudinal rows, smaller than those of the valve,
about 2*5 rows in 1 c.d.m. Length of valve, 5*5
to 2 1 c.d.m.
Marine, parasitic. Very rare in Belgium, and hitherto only found ill the washings of mussels.
England (W. Sin. ! Ralfs, Kitton, Mrs. Griffiths, Okeden) Ireland ; (W. Sm Dickie) ;
Channel Islands (Baxter Coll. No. 3825); France (Desmazieres) Finmark ;
(Cleve).
and Spitzbergen
I. nervosa Kutz. (Baa, p. 137, pi. 19, f. 5; W. Sm, S.B.D., ii.,
p. 52, pi. 47* ;
H.V.H.
Types, No. 485), plate 34, fig. 891.
Differs from the preceding by interior costas, which consolidate the valve
and are very visible in the girdle face.
Marine. Parasitic on other algae. Not yet found in Belgium, England (W. Sm. !
Kitton).
Ireland (O'Meara, Mrs. Lvon, Moore). Shetland Islands (Edmonstone), Denmark. Iceland
(C. Agardh).
a.
Fig. 176.
Terpsitw'e musica.
a. Valve view.
b. Girdle view.
II. Hemiaulide^e. Valves sim-
ple or septate, often showing various
abnormal inflations or with apices
raised into a mucronate point.
GENUS 117. TERPSINOE EHR.,
1843.
Valves furnished with transverse costse,
without spines or any trace of pseudoraphe.
Frustules showing in girdle view
transverse costae, capitate, resembling
musical notes. Frustules united in bands.