ANATOMY OF THE LEMUROIDEA. Ji 
preface of which bears the date 1849), has figured a single, but very large, supracostal 
muscle in L. varius, pl. 69. fig. 2. 18; this he has called sternocostal. 
The first supracostalis muscle in Lemur catta arises by tendinous fibres from the 
cartilages of the fourth, fifth, sixth, and seventh ribs, and is inserted into the first rib 
just external to the origin of the subclavius, and crossing over the anterior end of 
the rectus (Pl. IV. fig. 12, Sp.co'). The second supracostal muscle in the same animal 
arises from the fourth and fifth ribs, just external to the outer ends of their cartilages, 
and closely connected with the fourth and fifth digitations of the serratus magnus. It is 
inserted, by a distinct though delicate tendon, into the first rib (PI. IV. fig. 12, Sp.co’). 
This muscle was absent in our specimen of L. varius, and, if present, not distinct in 
L. nigrifrons. 
In L. aanthomystax, on the contrary, the first supracostal, as described in L. catta, 
was present, and with nearly the same attachments. What might represent the second 
supracostal we were rather doubtful about. A second small slip did exist on the right 
side only; but this lay rather to the inner side, and therefore probably may have been 
a portion of the sternal prolongation of the rectus muscle. 
In Galago crassicaudatus and in @. allenii a few fibres only appear to pass forwards 
and outwards over the anterior prolongation of the rectus from the third to the first rib. 
This strip may be considered the first supracostal muscle (Pl. V. fig. 16, Sp.co). 
We found a supracostal in Nycticebus tardigradus extending from the third to the 
first rib. 
In the Potto, Van Campen found two supracostals (as already mentioned), and has 
well represented them. 
Such muscular slips are not recorded by Burmeister in Zursius, nor by Owen in 
Cheiromys; but in our specimen of the latter we find one remarkably large supracostal, 
having a tendinous origin from the cartilage of the third rib close to the sternum, and 
inserted into the first rib just external to the insertion of the subclavius, and just over the 
external half of the insertion of the rectus. The scalenus is immediately external to it. 
TRIANGULARIS STERNI.—In Lemur catta this is represented by a tolerably thick and 
continuous muscular layer reaching from the ensiform cartilage to the second rib. 
Inwardly it is attached to the sternum; and outwardly, by a series of serrate prolonga- 
tions, it goes to the costal cartilages from the seventh to the second. It is noticed by 
Burmeister in Tarsius. 
In Cheiromys we found this muscle well developed, arising as usual and passing from 
the sternum by digitations to the cartilages of the ribs, reaching from the third rib to 
the eighth inclusive. 
EXTERNAL OBLIQUE'.—This is a very elongated muscle which arises by digitations from 
the ribs, from the fifth to the twelfth inclusive, the three uppermost digitations being 
1 Very imperfectly represented by Cuvier in L. varius, pl. 68. fig. 1. 13, and in Loris gracilis, pl. 67. figs. 1 
and 2. 13. 
H 2 
