Reviews—Professor Sollas—I chthyosawurus Skull. 571 
for the determination of longitude is likely to increase in usefulness. 
Good examples of the work done with it have lately been given in 
the Geographscal Journal and elsewhere. 
REVIEWS. 
T—Taer Sxurn or Journos URUS, STUDIED IN SERIAL SECTIONS. 
By Professor W. J. Sotras, F.R.S. Phil. Trans., ser. B, vol. ceviii, 
pp. 63-126, with 22 text-figures and 1 plate, 1916. 
N this paper Professor Sollas gives a detailed account of the 
results of his method of serial sections applied to the skull of an 
Ichthyosaur, probably a variety of J. communis. No less than 
520 sections were prepared, photographed, and modelled in wax, 
and the resulting reconstruction gives a clearer idea of the details - 
of the structure of the skull than has hitherto been attainable. 
The relations of the roofing bones of the skull, that unite by 
extensively overlapping sutures, are now for the first time made 
clear, and the presence of a septo-maxillary element is demonstrated ; 
in the lower jaw the presence of the gonzale (prearticular) is shown. 
Professor Sollas has met with the usual difficulty in determining 
the relative position of the bones forming the auditory capsule, the 
existence during life of extensive areas of cartilage between them 
resulting in their displacement when putrefaction took place. He 
puts the pro-otic low down, below the opisthotic and in contact with 
the basi-occipital, a position which seems inconsistent with the share 
which this element must have taken in helping to enclose the 
auditory labyrinth. 
Another point of special interest is the presence of a series of 
structures which are regarded as the remnants of a hyobranchial 
apparatus. Not only is this interpretation an improbable one, but 
the facts seem capable of a simpler explanation. The elements 
(marked a and 6 in fig. 17) which are regarded as branchials 
closely resemble in form the upper bifurcated ends of cervical ribs, 
while those marked s.d. may be halves of a neural arch. Professor 
Sollas admits that these bones lie dorsal to the hyoids, and further- 
more notes the presence in the specimen of the displaced centra of 
the atlas, axis, and third cervical, so that it therefore seems at least 
possible that the presumed branchial bones are displaced appendages 
of these vertebra. 
The paper is illustrated with twenty-two text-figures, mostly of 
sections of the skull, and a plate giving figures of the basi-occipital 
and basisphenoid, both of the reconstructed skull and of other 
specimens. Some diagrammatic figures of the various bones might 
have been added with advantage. 
The paper as a whole is a valuable contribution to our knowledge, 
and the author is to be congratulated on the successful application of 
his elaborate and laborious method of investigation to a fresh subject. 
C. W. A. 
