﻿13 51 



of the lachides are considerably longer in A. strigata and punciiilata tlian in 

 scutata* '. 



Endoskeleton. 



The vertebral column (cf. Pi. Il, fig. 1) is formed of 20 verlebræ; of these 

 I count 8 as abdominal verlebræ, 12 as caudal. Of the abdominal vertebræ the 

 first 6 are much elongated, especially the 2nd to the fifth; the 2nd, 3rd and 4th 

 are each almost as long as the rest of the vertebræ together, so that the elongated 

 region is nearly four limes as long as the whole of the remainder. In a small 

 specimen of A. strigata the measurements are approximately as follows: 



length of the whole column ca. 47 mm. 



— - body of 1st vertebra 35 — 



_ - — - 2nd — 7 — 



_ - — - 3rd — 8 — 



— - — - 4th — 8 — 



_ . _ - 5th — 6-5 — 



_ . _ . 6th — 4 — 



— - elongated part, thus 37-0 — 



— - posterior 14 vertebræ together ca. 100 — 



In a (medium-sized) specimen of A. sciitata the measurements were: 

 length of the whole column ca. 52 mm. 



— - body of 1st vertebra 3-5 — 



_ . _ - 2nd — 8 — 



_ . _ -Sid — 9-5 — 



_ . _ - 4th — 9 — 



— - — - 5th — 7-5 — 



— - — - 6th — 3-5 - 



— - elongated part, thus 41 — 



— - posterior 14 vertebræ ca. 11 — 



Vertebral arches. The arch of the first vertebra is quite low, simple; 

 from its posterior margin projects a long, thin spinous process, which rests for a 

 long distance on a part of the upper margin of the next vertebral arch; its poste- 

 rior point reaches almost to llie centre (in scutata) or a good bit behind the centre 

 (strigata) of the following vertebra. True transverse processes are lacking on the 

 first vertebra, but a short, thick lateral process on each side under the anterior 

 margin of the arch forms an articulation with a corresponding pit in the exocci- 

 pilal and can possibly be regarded as an articular process. On the following 

 vertebræ, 2 — 17 inclusive, the arch is divided into an anterior (PI. II, fig. 1, a) and 

 a posterior (b) part, situated respectively over the anterior and posterior part of 

 the centrum; the spinous process arises from the posterior part of the arch and 



*l This and the succeeding notes, marlied with numbers, will be found later after the description 

 of Centriscus 



