608 
DR. GUNTHER ON THE ANATOMY OF HATTEEIA. 
The sternum (fig. 26, a) does not essentially differ from that of other Lizards ; it is a five- 
sided plate with a very thin ossified layer imbedded in its cartilaginous substance ; no 
division into lateral halves is perceptible. Its hinder margin passes into a broad ligament 
connecting it with the first abdominal rib, to the posterior lateral margins the hsemapo- 
physes of the first three ribs are joined; the anterior lateral margins are entirely car- 
tilaginous, and grooved for the reception of the coracoid (fig. 26, e d ) ; and, finally, at its 
front angle enters the episternum (fig. 17, b; fig. 26, b), which is very long, styliform, 
in continuity with a median keel of the sternal plate, and terminates in a transverse bar 
which is suturally united with the clavicles (fig. 17, c; fig. 26, c). 
The eleven posterior ribs are connected by means of their double hsemapophyses with 
a series of bones crossing the abdominal region and situated in the subcutaneous liga- 
mentous tissue extending from the sternum to the pelvis (fig. 26). This system of bones 
is similar to, but essentially different from, that observed in Crocodiles and some Lizards 
( Chamoeleon , Polyclirus , &c.), known as abdominal ribs or abdominal sternum, and con- 
sidered to be the ossified inscriptiones tendinese of the abdominal muscles. 
The first point of interest is, that in Hatteria the number of these abdominal ribs 
does not equal that of the corresponding true ribs and vertebrae, being nearly double 
that number (I have counted from twenty-five to twenty-six) ; it equals rather the 
number of transverse series of plates into which the external integument of the abdomen 
is divided, so that each abdominal rib runs along, and is firmly attached by tissue to, the 
anterior margin of one of those transverse series of plates. Each abdominal rib has the 
form of an angular, thin, very slender bone, tapering at the extremities, and somewhat 
dilated at the angle, which is directed forwards and obtuse. The angles of all these ribs 
lie in the same line, in the median line of the abdomen. Each consists of three bones, 
united by the closest juxtaposition — a central and a pair of lateral, the lateral being 
about as long as one of the halves of the central; however, these three bones are so 
firmly united that it is very difficult to separate them*. Normally the ribs are entirely 
separate from one another, and only exceptionally two or three coalesced by a narrow 
osseous strip in the median line. Every alternate abdominal rib (fig. 20) is suspended 
from the hsemapophyses of a pair of ribs, the suspension being effected by a short 
ligament in which the produced extremity of the dilated piece of the hsemapophysis 
terminates. The point of attachment is on the inner side of the abdominal rib, near 
the junction of its central and lateral pieces. The intermediate abdominal ribs are 
“ floating,” but otherwise not distinguished from the others. 
* The first example examined by me showed a very curious anomaly as regards the union of the three bones 
of which the abdominal ribs consist ; they were united by joints. That these joints are not the result of some 
accident — of fracture of the ribs at a former period — is proved by the circumstance that they exist only in every 
alternate rib, viz. in those which are connected with hsemapophyses, and, secondly, that they occupy exactly the 
same place, namely, at a short distance from the attachment of the haemapophysis, towards the median line of 
the belly. The intermediate abdominal ribs have no joints, their bones being juxtaposed as I have described 
above. I cannot offer any explanation of this singularity, which I must consider anomalous, not having met 
with it in five other examples. It is represented in fig. 20. 
