538 ME. JAMES JOHNSTONE ON THE 



of it extended some little distance upwards along the ventral aide 

 o£ the trachea and then died out. Most of the organ lay posterior 

 to the first rib. It was most massive at about the point of bifur- 

 cation of the carotids, and consisted there of six lobes separated 

 by fatty connective tissue. Thence it spread out as a thin sheet 

 posteriorly and laterally, so that in the more posterior sections 

 its extreme lateral edges touched on the one side the trachea, 

 and on the other the oesophagus, dorsal to the pericardium. 

 About halfway between the base and apex of the heart it was 

 reduced to a mere vestige on one side. 



In this specimen there were indications of two types of histo- 

 logical structure in the thymus : on the right side there was a 

 lobe almost co-extensive with the rest of the gland, from which it 

 di:ffered in showing a more defiuite capsule (as a matter of fact no 

 capsule existed in the other lobes of the thymus, which at almost 

 every point was in contact with a layer of fatty connective tissue), 

 no division into cortical and medullary portions, and a very 

 abundant blood-supply, capillaries permeating all its substance. 



DidelpJiys murina. 



My only example was a pouch-specimen of about 2-5 centim. in 

 length. Hair was found all over the surface of the body, and 

 ossification had well advanced. The head had been removed, but 

 the most anterior sections showed most of the submaxillary gland 

 and the thyroid. I was unable to observe any indication of a 

 cervical extension of the thymus or of a detached cervical 

 portion. The gland itself lay entirely within the transverse 

 plane passing through the junctions of the first and fourth ribs 

 with the sternum. It was lour-lobed, the greatest elongation of 

 the lobes being dorso-ventral. Posteriorly it was reduced to thin 

 lateral sheets lying on the sides of the pericardium. 



II. Dasturid^. 



I have examined four specimens of this family — a full-grown 

 Dasyurus viverrinus^ a full-grown Tliylacinus, a mammary foetus 

 of Dasyurus, species indeterminable, and a full-grown specimen 

 of AntecMnomys lanigera. 



Dasyurus viverrinus. 



The heart (PI. 37. fig. 1) was almost entirely surrounded by 

 fat (/), two large lateral masses of which extended from its base 



