“MARSHALL: ALTERATIONS IN ‘BRITISH CONCHOLOGY:’ 37 
In the ‘ Lightning’ Report, Jeffreys has extended these 
remarks. He there observes :—‘I am now inclined to 
separate Z7zforis from Cerithium by reason of the differences 
in the apex or embryonic part of the shell, and in the 
former having a short basal canal instead of a mere groove 
or notch. ‘The spire [tip] of Z7z/oris is finely blunted ; in 
Cerithium itis blunt. In 7Z7zfor’s the apical whorls are 
much narrower in proportion and are closely striated 
lengthwise, and the canal is small and nearly closed, as in 
Murex ; in Cerithtum the groove is comparatively large and 
open. According to Meyer and Mobius there is also a 
characteristic distinction between the animals and odonto- 
phores of the two genera. The snout in Z7zforis and 
Cerithiopsts is retractile, while in Cer/thium it is contractile. 
Sis Triforis appears to be congeneric with 
Cerithiopsts and to belong to the same family. When the 
shells of Z: perversa and C. tubercularis are exhibited, one 
before a mirror and the other not, it will be seen that almost 
the only differential character consists in the lower or basal 
portion of the mouth being more closed in Zrzforcs than 
in Certthtopsts.’ 
The description of the apical whorls of Z! perversa 
given by Dr. Watson in the ‘Challenger’ Report does not 
agree with that of Dr. Jeffreys in ‘ British Conchology.’ 
While the latter describes them as exhibiting ‘very minute 
and numerous longitudinal strize, which are encircled in the 
middle by a delicate spiral thread in such a manner as to 
make them appear keeled or angulated, and the nucleus is 
smooth and glossy,’ Dr. Watson says that these apical 
whorls ‘are beset with close-set and numerous riblets, and 
they have two close-set spirals at the carina, while the ex- 
treme apex has about seven spiral scratches, parted by 
roughened threads.’ This discrepancy may be accounted 
for by the former writer habitually using no higher power 
than a Coddington, while the latter used a microscope. 
