MR.  E.  T.  BENNETT  ON  THE  CHINCHILLID^. 
49 
its  surface.  It  adheres  to  the  skin  with  a  tenacity  which  adds  much  to  its  value  in  a 
commercial  and  economical  point  of  view,  and  would  alone  give  it  a  commanding  su- 
periority over  that  of  the  Lagotis.  It  has  a  similar  dusky  colour  at  the  base,  with  short 
tips  of  greyish  white,  and  with  scarcely  a  shade  of  the  yellowish  brown  tinge,  except 
occasionally  towards  the  haunches  and  on  the  croup,  and  then  only  very  slightly 
marked.  The  under  surface  is  mottled  like  the  upper,  but  with  a  much  greater  pro- 
portion of  white.  On  the  under  surface  of  the  tail,  the  short  adpressed  hairs  are  of  a 
dirty  yellowish  brown,  while  the  much  longer  and  more  bristly  hairs  of  the  sides  and 
upper  surface  are  whitish  at  their  base,  brownish  black  from  thence  through  the  greater 
part  of  their  length,  and  yellowish  brown  at  the  tip,  with  the  exception  of  the  tuft  at 
the  extremity,  which  appears  of  an  almost  uniform  brownish  black,  the  tips  being  less 
distinguishable  in  colour  than  in  the  rest. 
For  the  external  characters  of  Lagostomus,  as  I  have  not  at  present  the  skin  to  refer 
to  and  neglected  formerly  to  take  notes  of  it,  I  must  refer  to  the  paper  of  MM.  Isidore 
GeofFroy-Saint-Hilaire  and  Dessalines  D'Orbigny  fils,  and  to  the  work  of  M.  Lesson 
before  quoted. 
It  may  be  also  proper  to  mention  here  the  supposed  second  species  of  Chinchilla,  de- 
scribed by  M.  Isidore  GeofFroy-Saint-Hilaire,  in  the  paper  just  referred  to,  from  skins 
in  the  possession  of  some  Parisian  furriers,  without  legs,  ears,  or  tail.  This  animal 
would  appear,  from  the  description  there  given,  to  be  indeed  nearly  related  to  Chin- 
chilla, and  even  in  some  respects  to  approach  my  Lagotis.  But  the  colours  assigned 
to  it  (yellow  tinged  with  greenish  and  slightly  undulated  with  black  above,  and  bright 
golden  yellow  shaded  with  reddish  brown  below,)  are  too  strikingly  different  from  those 
of  Lagotis  to  admit  of  their  being  regarded  as  the  same.  It  is  further  said  that  in  the 
species  in  question,  the  Callomys  aureus,  Isid.  G.-St.-Hil.,  the  base  of  the  fur  is  brown, 
while  in  Chinchilla  it  is  dark  grey.  In  Lagotis,  on  the  contrary,  the  base  of  the  fur  is 
only  a  shade  lighter  than  in  the  Chinchilla,  and  is  of  that  peculiar  hue,  which,  from  its 
near  approach  to  black,  without  partaking  of  any  decided  colour,  I  have  generally  been 
in  the  habit  of  denominating  dusky,  or  when  deeper  dusky  black.  It  has  not  the 
slightest  tendency  towards  browm. 
The  anatomical  examination  of  Lagotis  and  Chinchilla  gave  the  following  results.  In 
both  animals,  on  laying  bare  the  face,  Meckel's  muscle  appeared  very  distinct  from  the 
masseter  at  its  anterior  termination,  but  was  shown  on  further  examination  to  be,  as 
usual,  only  a  developed  portion  of  that  muscle.  The  parotid  gland  extended  in  a  flat- 
tened form  along  the  neck  ;  the  submaxillary  was  more  compact.  The  digastric  muscle 
was  strong,  and  had  a  slightly  tendinous  appearance  in  the  middle,  where  it  was  con- 
nected with  the  OS  hyoides.  The  sterno-mastoid  and  cleido-mastoid  muscles  were 
distinct ;  and  the  interarticular  cartilage  between  the  clavicle  and  sternum  was  remark- 
ably long,  although  less  so  than  in  the  Porcupine,  measuring  in  Lagotis  three-eighths, 
in  Chinchilla  about  one  quarter,  of  an  inch.    The  thyroid  gland  ascended  on  each  side 
VOL.  I.  H 
