CHITONID. 339 
so imitate the Iceland fishermen, who pretend that the “sea 
bugs” are an effectual remedy against this malady, and also 
that they quench thirst. Perchance the deglutition of these 
strange bolusus might by anticipating the evil rob a sea-passage 
of its horrors.—JEFFREYsS, British Conchology. 
Section I1.—Chitones Regulares. 
Head- and tail-plates similarly articulated. 
A. Leptoidea. 
Insertion-plates obsolete or, if present, unslit. 
(Eatinct Forms.) 
The secondary and tertiary Chitons all belong to recent genera. 
The following are all paleozoic. A large number of the fossils 
described as Chitons (for instance Sulcochiton Grayi, Ryckholt) 
are not mollusks ; many of them being valves of Balani or frag- 
ments of isopod crustaceans. 
HELMINTHOCHITON, Salter. Shell elongated, regular; mucro 
regular, subcentral; terminal valves not sinuated ; apophyses 
unknown. Distr.—2sp. Silurian, Devonian; Europe. C.Griffithi, 
Salter (Ixxxv, 58). 
GRYPHOCHITON (Gray), Carpenter. Shell elongated; lateral 
laminz none, suturals small, separated by a wide, simple sinus ; 
mucro inecurved like the beak of a Gryphea; posteriorly and 
anteriorly strongly sinuated. Distr.—4 sp. Carboniferous; 
Belgium. (CC. priscus, Munster (Ixxxv, 70). 
CHONECHITON, Carpenter. Shell Leptoidal, the central valves 
like Gryphochiton, the last with posterior mucro, infundibuli- 
form. Distr.—Carboniferous; Belgium. (©. viseticola, Ryck. 
(bexxcy 39): 
PRISCOCHITON, Billings. Leptochiton, with posterior lamina 
excavated within. Distr.—L. Silurian; Canada. C. Canadensis, 
Billings (Ixxxv, 64-66). 
PTEROCHITON, Carpenter. Shell elongated, Leptoidal; valves 
laterally excavated, posteriorly acuminated ; last valve regular, 
the mucro Ischnoidal; anterior valve (usually ?) sinuated ; apo- 
physes large, sinus wide. Distr.—6 sp. Devon.; Ireland, 
Belgium, ete. C. eburonicus, Ryck. (lxxxv, 67). 
LORICITES, Carp. Related to Lorica, from which it differs in 
the absence of laminz of insertion. Fossil. Type, C. concen- 
tricus, Koninck. , 
PROBOLZUM, Carpenter. Shell Leptoidal, elongated, largely 
projecting ; central valve with the central area extending in front 
of the jugum ; anterior valve sinuate, posterior valve (7). Among 
recent forms this comes nearest to Katherina, but the difference 
is still extremely great. Distr—Devonian of Vilmar.  P. vor- 
rugatum, Sandb. ron *F ; 
