Literary Notices. vii 
Its subsequent history varies greatly in different Orders. In the 
Carnivora, Ungulata, Chiroptera, and many other mammals the sulcus 
becomes concurrent with another element of vastly less morphological 
importance, which I have called the ‘‘intercalary sulcus.” The 
calcarine-intercalary complex forms the ‘‘splenial sulcus” of these 
brains. 
In most mammals, with the exception of the Primates, the tension 
of the growing cortex in the infracalcarine region is relieved by the 
downward extension of the calcarine sulcus to the neighbourhood of 
the rhinal fissure. 
In the Anteaters, Sloths, Pangolins, Lemurs, and Apes the calca- 
rine sulcus always remains separate from the intercalary sulcus, and the 
latter joins with the genual sulcus in the Primates to form the calloso- 
marginal sulcus. 
In many Carnivores and Ungulates (and in large mammals gener- 
ally) one or more deep sulci make their appearance behind the calcarine 
sulcus, and in most cases one of these,-which we may call the ‘‘retro- 
calcarine”’ sulcus, is deeper and more constant than the others and 
often joins the calcarine sulcus. ‘This is seen to advantage in the brain 
of the Lion, Tiger, or Seal among Carnivores, or in the Horse, Camel, 
or Ox among Ungulates. This retrocalcarine sulcus is obviously of 
very minor morphological importance in comparison with the true cal- 
carine sulcus, and this is shown by its adaptability to the varying me- 
chanical conditions prevalent in different Orders.’ In the Primates 
both the retrocalcarine (Cunningham’s ‘‘ posterior calcarine”’) and the 
true calcarine (Cunningham’s ‘‘ anterior calcarine’’) sulci tend, as a re- 
sult of the occipital extension of the hemisphere, to become horizontal 
and in most cases become concurrent. In the more rapidly expanding 
human brain it often happens that the two sulci do not exactly meet, 
as they generally do in the Apes. Cunningham is thus led to the be- 
lief that the human brain differs from the Simian brain in possessing a 
retrocalcarine sulcus; but there can be little doubt that the so-called 
*‘calcarine”’ sulcus of the Apes is really a fusion of the retrocalcarine 
and true calcarine sulci, and therefore does not materially differ from 
the human calcarine complex. If the caudal extremity of this ‘‘calca- 
rine complex” be studied in the Apes it will be found to be exceedingly 
variable and unstable, so that one cannot regard it as a part of the true 
calcarine, which is an exceedingly stable sulcus. 
By true ‘‘calcarine sulcus” I mean that depression which corre- 
sponds to or produces the calcar avis. As Flower long ago pointed 
out (Phil. Trans. 1862, p. 198, footnote), the presence of a posterior 
attempted to extend its supposed homologies to the Anthropoid pattern so far 
as to utterly discredit any value that may attach to their recognition of its 
calcarine nature. 
1 At the same time the fact that it develops in the midst of the region in 
which Vicq d’Azyr’s stripe occurs in the Primates, and which represents the 
visual ‘‘centre,” lends a special interest to this sulcus, which obviously accom- 
modates the expanding visual cortex. 
