FEBRUARY 1, 1884.] 
Orthoceras pleurotomum Barr. (Syst. sil., pl. 
296), which are undeniably transitions to true 
Orthoceras in their striae of growth and posi- 
tion of siphon. There is therefore convincing 
evidence in the structures of these Cambrian 
shells that the Ammonoidea, with their distinct 
embryos, arose from the orthoceran stock, and 
passed through a series of forms, in times, 
perhaps, preceding the Cambrian, which were 
parallel to those characteristic of genetic series 
among Nautiloidea; viz., straight, arcuate, 
gyroceran, and nautilian. 
The researches of Emmons and Marcou in 
this country, and the discovery of ten thousand 
feet or more of stratified rocks under the Cam- 
brian by the U.S. geological survey, and the 
inferences of Bigsby from the extended study 
of Silurian and Devonian fossils, are begin- 
ning to place the probable existence of a pre- 
paleozoic period beyond question, in spite of 
the really grand opposition and world-wide 
researches of Barrande. The study of the 
tetrabranchs teaches us, that, when we first 
meet with reliable records of their existence, 
they are already a highly organized and very 
varied type with many genera, and that the 
name ‘ paleozoic,’ as applied to these first rec- 
ords, is a misnomer. There was a protozoic 
period ; and the tetrabranchs, like their succes- 
sors, certainly must have had ancestors which 
preceded and generated them in this period, 
but of which we are at present necessarily igno- 
rant. Whatever the future may have in store 
for us we cannot now predict; but at present 
the search for the actual ancestral form, though 
necessary, is nevertheless not hopeful. We 
can, however, rely upon the facts of embry- 
ology, and predict without fear of failure, that, 
when our k owledge makes this prototypical 
form known, it will have a decided resem- 
blance in structure and in aspect to the earlier 
stages of the shell as observed in the fossil 
cephalopods. 
(To be continued.) 
SCALES OF COLEOPTERA. 
SomE of the more interesting forms of scales of Cole- 
optera described in the paper by Dr. George Dimmock, 
noticed in Science, i. 455, are shown in the annexed 
figures. The scales of the carpet-beetle, Anthrenus 
scrophulariae, and of the museum pest, A. varius (fig. 
1), resemble in general form those of many Lepidop- 
tera, as do also the scales of Valgus squamiger (fig. 3). 
The scales of V. squamiger are, however, hairy, in fact, 
almost shaggy. ‘The scales of Hoplia coerulea (fig. 2) 
vary from round to lanceolate, those of the dorsal sur- 
face being transparent yellow when viewed by trans- 
mitted light, and blue by reflected light. Those of 
SCIENCE. 
127 
the ventral surface are purplish, purplish red, red, 
bluish, and colorless by transmitted light, while by 
reflected light they are silvery white, with at times a 
tendency to metallic green. The scales of the dorsum 
are smooth, filled with fine reticulations (fig. 2, d), 
but those of the ventral portions and of the tip of the 
: 
i) 
i | 
La 
MIG. 5: Fie. 6. 
EG oat Fig. 8. 
Fie. 1.—Scales of Anthrenus: a, of A. scrophulariae; 6, 
arrangement of same on portion of an elytron; c, scales of A. 
varius. Enlargement: @ and c, 100 diam.; 0, 50 diam. 
Fic. 2.—Scales of Hoplia coerulea; a, from elytron; 0, from 
under side of thorax; c, from femur; d, fine structure to be 
seen in a, with high powers. Enlargement: a, b, and c, 100 
diam.; d, 500 diam. 
Fie. 3.— Scale of Valgus squamiger. Enlarged 100 diam. 
Fie. 4.— Different forms of scales from Chalcolepidius rubri- 
pennis. Enlarged 100 diam. 
Fie. 5.— Scales of Alaus oculatus: a, brown scale; 0 and c¢, por- 
tions of white scales to show cross-bands; d, transverse sec- 
tion of a brown scale. Enlargement: a, 100 diam.; 6 and c, 
300 diam.; d, 500 diam. 
Fig. 6.— Seales and hair of Plinus? rutilus: a and b, scales from 
elytron; c, hair from elytron. Enlarged 100 diam. 
Fie. 7.—Scale of Clytus robiniae. Enlarged 100 diam. 
Fie. 8.— Scales of Entimus imperialis: on a, 0, and c¢, vertical 
lines indicate blue, horizontal lines indicate carmine red, and 
oblique lines yellow; where two kinds of lines cross, one 
color is tinged with the other; on d ard e the fine lines repre- 
sent the finer striation of the inner layer of the scales. En- 
largement: a, 6, and c, 100 diam.; d@ and e, 300 diam. 
abdomen are covered with fine hairs representing the 
branches of the ordinary hairs of scarabaeidous bee- 
tles. The scales of Chalcolepidius rubripennis, an 
elaterid, are transparent brown when seen by trans- 
mitted light, but by reflected light appear bronzed 
blue, green, or red. Their form is seen in fig. 4. 
The black and white scales of Alaus oculatus (fig. 5), 
which give rise to the entire figuration of that curi- 
ously marked elaterid, although not of especially pe- 
