259 
periodo di sua floridezza e maturitä non ha bisogno pel suo schema 
istologico di nessuna parete, ed in ogni modo la pellucida, quando 
esiste, © un involucro accessorio di nessuna importanza per |’ uovo in 
ordine alla sua piena costituzione ed alle sue fasi evolutive. 
Napoli, Febbrajo 1890. 
Nachdruck verboten. 
On the skull and Visceral Skeleton of the Greenland Shark, 
Laemargus microcephalus. 
By Puiu J. Were, M. B, 
Lecturer in Zoology, University College of North Wales, Bangor. 
I intend here, to give an abstract of a paper, on the cranial 
skeleton of this shark, read before the Royal Society of Edinburgh 
some time ago. 
In my paper which will be published in extenso, it will be noted 
that I have followed as far as possible, the lines laid down by GEGEN- 
BAUR!) for the description of the skulls of Elasmobranchs, and I have 
compared the cranial parts of Laemargus with those of other Sela- 
chians when I deemed that necessary. 
In the cranio-vertebral connection of the skull of Laemargus, it 
is seen, that the anterior portion of the first vertebra is wedged in 
at the hinder part of the occipital region, that the mesial portion of 
the vertebral centrum is continuous with the cranium, while its la- 
teral portions, although firmly bound to the skull are distinct there 
from, and that the neural arch of the vertebra enters freely within 
the foramen magnum. 
The occipital crest which passes from the hinder part of the pa- 
rietal fossa to the upper margin of the foramen magnum is somewhat 
prominent. 
Each cranio-hyoid depression presents two articular surfaces for 
the heads of the hyomandibular cartilage. 
In the orbital region the prominent supraorbital ridges with three 
preorbital and postorbital processes are noteworthy features. 
1) Untersuchungen zur vergleichenden Anatomie der Wirbeltiere, 
von Dr. Cart GEGENnBAUR. — Das Kopfskelett der Selachier, als Grund- 
lage zur Beurteilung der Genese des Kopfskelettes der Wirbeltiere. 
18* 
